CHAP. VIII

 

Reflections on the preceding Experiments.

 

            FROM the foregoing experiments, it appears, that females, as well as males, have a seminal fluid containing bodies in motion; that these moving bodies are not real animals, but only organic living particles; and that these particles exist not only in the seminal fluids of both sexes, but in the flesh of animals, and in the seeds of vegetables.  To discover whether all the parts of animals and all the seeds of plants contained moving organic particles, I made infusions of the flesh of different animals, and of the seeds of more than twenty different species of vegetables; and, after remaining some days in close glasses, I had the pleasure of seeing organic moving particles in all of them.  In some they appeared sooner, in others later.  Some preserved their motion for months, and others soon lost it.  Some, at first, produced large moving globules, resembling animals, which changed their figure, split, and became gradually smaller.  Others produced only small globules whose motions were extremely rapid; and other produ- [212] ced filaments, which grew longer, seemed to vegetate, and then swelled, and poured out torrents of moving globules.  But it is needless to give a detail of my experiments on the infusions of plants, especially since Mr Needham has published his excellent and numerous observations on this subject.  To this able naturalist I have read over the preceding treatise; I have often reasoned with him on the resemblance between the moving bodies in infusions of the seeds of vegetables, and those in the seminal fluids of male and female animals.  He thought my views well founded, and of sufficient importance to merit a farther discussion.  He, therefore, began to make experiments on the different parts of vegetables; and I acknowledge, that he has brought the ideas I communicated to greater perfection, than could have been done by me.  Of this I could give many examples:  But I shall confine myself to one, because I formerly pointed out the fact in question, which he describes in the following manner.

 

            To ascertain whether the moving bodies which appear in infusions of flesh were real animals, or only, as I had imagined, organic moving particles, Mr Needham thought that an examination of the jelly of roasted meat would determine the question; because, if they were animals, the fire would destroy them, and, if not, they would still be perceptible, in the same manner as when the flesh was raw. Having, for this purpose, ta- [213] ken the jellies of veal and of other kinds of roasted meat, he put them in glasses filled with water, and carefully corked the bottles.  After some days infusion, he found in the whole of the liquors an immense number of moving bodies.  He showed me several of these infusions, and, among others, that of the veal jelly, which contained moving bodies very similar to those of man, the dog, and the bitch, after they had lost their tails or threads.  Though they changed their forms, their motions were so similar to those of animals swimming, that, whoever saw them for the first time, or had been ignorant of what has been formerly remarked concerning them, would certainly have apprehended them to be real animals.  I shall only add, that Mr Needham has established, by numberless experiment, the existence of moving organic particles in all the parts of vegetables, which confirms what I have alledged, and extends my theory concerning the composition and reproduction of organized beings.

 

            It is then apparent, that all animals, whether male or female, and every species of vegetable, are composed of living organic particles.  These organic particles abound most in the seminal fluids of animals, and in the seeds of vegetables.  Reproduction is effected by the union of these organic particles, which are detached from all parts of the animal or vegetable body, and are always similar to the particular species to which [214] they belong; for their union could not be accomplished but by the intervention of an internal mould, which is the efficient cause of the figure of the animal or vegetable, and in which the essence, the unity, and the continuation of the species consists, and will invariably continue till the end of time.

 

            But, before drawing general conclusions from the system I have established, some objections must be removed, which will contribute still farther to illustrate the subject.

 

            It will be demanded of me, why I deny these moving bodies to be animals, after they have uniformly been recognized as such by every man who has examined them?  It may likewise be asked, How is it possible to conceive the nature of living organic particles, unless we allow them to be real animals?  And to suppose an animal to be composed of lesser animals, is nearly the same idea, as when we say, that an organized body is composed of organic living particles.  To these questions, I shall endeavour to give satisfactory answers.

 

            It is true, that almost all observers agree in regarding the moving bodies in the seminal fluid as real animals.  But it is equally certain, both from my experiments, and those of Mr Needham upon the semen of the calmar, that these moving bodies are beings more simple and less organized than animals.  [215]

 

            The word animal, in its common acceptation, represents a general idea, composed of particular ideas which we derive from particular animals.  All general ideas include many different ideas, which more or less approach or recede from one another; and, of course, no general idea can be precise or exact.  The general idea we have formed of an animal, may be derived from the particular idea of a dog, of a horse, and of other animals, from the power of volition, which enables them to act according to their inclination, and from the circumstances of their being composed of flesh and blood, from their faculty of chusing and of taking nourishment, from their senses, from the distinction of sexes, and from their power of reproducing.  The general idea, therefore, expressed by the word animal, includes a number of particular ideas, not one of which constitutes the essence of the general idea:  For there are animals which have no intelligence, no will, no progressive motion, no flesh or blood, and appear to be only a mass of congealed mucilage:  There are others, which cannot seek for their food, and only receive it from the element in which they exist; others have no senses, not even that of feeling, at least in a perceptible degree.  Some have no sexes, or have both in one individual.  There remains nothing, therefore, in the properties of an animal, but the power of reproduction, which is common to both the vegetable and animal.  It is from the [216] whole taken together that a general idea is formed; and, as this whole is composed of different parts, there must of necessity be degrees or intervals between these parts. An insect, in this sense, is less an animal than a dog, an oyster than an insect, and a sea-nettle, or a fresh water polype [sic], than an oyster:  And, as Nature proceeds by insensible degrees, we should find beings partaking of still less animation than a sea-nettle or a polype.  Our general ideas are only artificial methods of collecting a number of objects under one point of view; and they have, like other artificial methods, the defect of not being able to comprehend the whole.  They are in direct opposition to the procedure of Nature, which is uniform, insensible, and always particular.  It is to grasp a number of particular ideas under one word, of which we have no clearer notion that that word conveys; because, when the word is once received, we imagine it to be a line drawn between the different productions of nature; that every thing above this line is an animal, and every thing below it a vegetable, which is another word equally general, and employed as a line of separation between organized bodies and brute matter.  But, as has already been remarked, these lines of separation have no existence in nature.  There are bodies which are neither animals, vegetables, nor minerals, and every attempt to arrange them under either of these classes must be ineffectual.  [217]  For example, Mr Trembly, when he first examined the fresh water polypus, spent much time before he could determine whether it was an animal or a vegetable.  The reason is plain; this polypus is perhaps neither the one nor the other; and all that can be said is, that it has most resemblance to an animal:  And, as we are inclined to think, that every living being is either an animal or a plant, we believe not the existence of any organized body, unless it fall under some of these general denominations, although there must be, and in fact there are, many beings which belong neither to the one nor the other.  The moving bodies found in the seminal fluids, and in infusions of the flesh of animals, as well as in those of all parts of vegetables, are of this species:  We can neither rank them under animals nor vegetables; and no man in his senses will ever maintain them to be minerals.

 

            We may, therefore, pronounce, without hesitation, that the great division of natural productions into animals, vegetables, and minerals, comprehends not all material beings; since beings exist which can be included in neither of these classes.  Nature passes, by imperceptible steps, from the animal to the vegetable; but, from the vegetable to the mineral, the passage is sudden, and the interval great.  Here the law of imperceptible degrees suffers a violation.  This circumstance made me suspect, that, by exami- [218] ning Nature more closely, we should find intermediate organized beings, which, without having the faculty of reproduction, like animals and vegetables, would still enjoy a species of life and motion; beings which, without being either animals or vegetables, might enter into the constitution of both; and, lastly, beings which would consist of the first assemblages of the organic particles mentioned in the preceding chapters.

 

            Eggs constitute the first class of this species of beings. Those of hens and other female birds are attached to a common pedicle, and derive their nourishment and growth from the body of the animal.  But, when attached to the ovarium, they are not properly eggs; they are only yellow globes, which separate from the ovarium as soon as they acquire a certain magnitude:  Such is their internal organization, however, that they absorb nourishment from the lymph contained in the uterus, and convert it into the white, membranes, and shell.  Thus the egg possesses a species of life and organization.  It grows and assumes a form by its own peculiar powers:  It neither lives like an animal, nor vegetates like a plant, nor enjoys the faculty of reproduction. The egg, therefore, is a distinct being, which can neither be ranked with the animal nor mineral kingdoms.  If it be alledged, that the egg is only an animal production destined for the nourishment of the chick, and ought to be re- [219] garded as part of the hen; I reply, that eggs, whether impregnated or not, are always organized in the same manner; that impregnation changes only a part which is almost invisible; that it grows, and acquires a uniform figure and structure, both externally and internally, independent of impregnation; and, consequently, it ought to be considered as a separate and distinct being.

 

            This will be still more apparent, if we attend to the growth and formation of the eggs of fishes.  When the female deposits them in the water, they are properly but the rudiments of eggs, which, being lately separated from the body of the animal, attract and assimilate those particles that are fitted for their nourishment; and thus increase in size by mere absorption.  In the same manner as the egg of the hen acquires its white and membranes while floating in the uterus, the eggs of fishes acquire their white and membranes in the water; and, whether they are fecundated by the male’s shedding his milt upon them, or if they remain unimpregnated, they still arrive at full perfection.  It is plain, therefore, that eggs in general ought to be regarded as organized bodies, and forming a distinct genus from animals and vegetables.

 

            The organized bodies found in the semen of all animals, and which, like those in the milt of the calmar, are natural machines, and not animals, form a second species of the same genus.  [220]  They are properly the first assemblages of those organic particles so often mentioned; and, perhaps, they are the constituent particles of all animated bodies.  They appear in the semen of every animal, because the semen is only the residue of the organic particles which the animal takes in with its food.  The particles, as formerly remarked, assimilated from the food, are those which are most organized, and the most analogous to the animal itself:  It is of these particles that the semen consist; and, of course, we ought not to be surprised to find organized bodies in that fluid.

 

            To be satisfied that these organized bodies are not real animal, we have only to reflect upon the preceding experiments.  The moving bodies in the semen have been considered as real animals, because they have a progressive motion, and something similar to tails.  But, after attending, on the one hand, to the nature of this motion, which is suddenly finished, and never again commences, and, on the other, to the nature of the tails, which are only threads adhering to the moving body, we will begin to hesitate; for an animal goes sometimes slow, and sometimes fast; and it sometimes stops, and reposes, without moving at all.  These moving bodies, on the contrary, go always in the same direction at the same time; I never saw them stop and again begin to move; and, if they once stop, it is for ever.  I demand, if this continued motion, with- [221] out any repose, is common to animals; and if, from this circumstance, we ought not to doubt concerning the real animation of these moving bodies?  An animal should always have a uniform figure, as well as distinct members:  But these moving bodies change their figure every moment; they have no distinct members; and their tails are only adventitious matter, and no part of the individual. How, then, can they be esteemed real animals?  In seminal liquors, we see filaments which stretch out, and seem to vegetate; then they swell and produce moving bodies.  These filaments are, perhaps, of a vegetable nature; but the moving bodies which proceed from them cannot be animals; for we have no example of vegetables giving birth to animals.  Moving bodies are found in all animal and vegetable substances promiscuously.  They are not the produce of generation.  They have no uniformity of species.  They cannot, therefore, be either animals or vegetables.  As they are to be met with in every part of animals and of vegetables, but are most abundant in their seeds, is it not natural to regard them as the organic living particles of which animals and vegetables are composed, as particles which, being endowed with motion, and a species of live, ought to produce, by their union, moving and living beings, and, in this manner, form animals and vegetables?  [222]

 

            But, to remove every doubt upon this subject, let us attend to the observations of others.  Can the active machines discovered by Mr Needham in the milt of the calmar be regarded as animals?  Can we believe that eggs, which are active machines of another species, are also animals?  If we examine Leeuwenhock’s representations of the moving bodies found in many different substances, will we not be satisfied, at the first inspection, that they are not animals, since none of them have any members, but are uniformly either round or oval?  If we attend to what this famous observer has remarked concerning the motion of these pretended animals, we must be convinced that he was wrong in regarding them as real animals, and we will be more and more confirmed in the opinion, that they are only organic moving particles.  We shall give some examples.  Leeuwenhoek,* gives the figure of the moving bodies in the seminal fluid of a male frog.  This figure represents nothing but a thin, long body, pointed at one of the extremities.  Let us attend to what he says concerning it:  “Uno tempore caput, (that is, the largest extremity of the moving body), crassius mihi apparebat alio; plerumque agnoscebam animalculum haud ulterius quam a capite ad medium corpus, ob caudae tenuitatem, et cum idem animalculum Paulo vehementius moveretur (quod tamen tarde fiebat) quasi volumine [223] quodam circa caput ferebatur.  Corpus fere carebat motu, cauda tamen in tres quatuorve flexus volvebatur.”  Here we have the change of figure that I had observed, the mucilage from which the moving bodies with difficulty disengage themselves, the slowness of their motion before they escape from the mucilage, and, lastly, a part of the pretended animal in motion while the other is dead; for, a littler afterwards, he observes, “movebant posteriorem solum partem, quae ultima, morti vicinia esse judicabam.”  All this is repugnant to the nature of an animal, but exactly corresponds with my experiments, excepting that I never saw the tail move but in consequence of an agitation of the body.  Speaking of the seminal fluid of the cod, he says,* “Non est putandum omnia ankimalcula in femine aselli conttenta uno eodemque tempore vivere, sed illa potius tantum vivere quae exitui seu partui vicinioroa sunt, quae et copiosiori humido innatant prae reliquis vita carentibus, adhuc in crassa material, quam humor eorum efficit, jacentibus.”  If these are animals, why were they not all alive?  Why did those only live which were in the most fluid part of the liquor? Leeuwenhoek did not observe; that the thick part, instead of being a humor produced by the animalcules, is a mucilage which gives birth to them. If he had diluted the mucilage with water, he would at once have [224] given life and motion to the whole.  The mucilage itself is often nothing else than a mass of those bodies, which begin to move as soon as they can disengage themselves; and, of course, this thick matter of mucilage, instead of being a humour produced by the animalcules, is only a congeries of the animals themselves, or rather, as formerly remarked, the matter of which they are formed.  Speaking of the semen of the cock, Leeuwenhoek, in his letter to Grew, says,* “Contemplando materiam (seminalem) animadverti ibidem tantam abundantiam viventium animalium, ut ea stuperem; forma sue externa figura sua nostrates anguillas fluviatiles referebant, vehementissima agitatione movebantur; quibus tamen substrati videbantur multi et admodum exiles globuli, item multae plan-ovales figurae, quibus etiam vita posset attribui, et quidem propter earumdem commotions; sed existimabam omnes hasce ommotiones et agitations provenire ab animalcules, sicque etiam res se habebat; attamen ego non opinione solum, sed itiam ad veritatem mihi persuadeo has particulas, planam et ovalem figuram habentes, esse quaedam animalcula inter se ordine suo disposita et mixta, vitaque adhuc carentia.”  Here we have animalcules, in the same seminal fluid, of different forms; and I am convinced, from my own experiments, that, if Leeuwenhoek had observed those oval bodies [225] attention, he would have perceived that they moved with their own proper force, and, consequently, that they were as much alive as the others.  This change of figure, it is true, exactly corresponds with what I had observed:  But it does not indicate a uniform species of animals; for, in the present example, if the bodies having the figure of a serpent were genuine spermatic animalcules, each of which was destined to become a cock, and therefore implies a uniform and invariable organization, what was the end and destination of those of an oval figure?  He, indeed, afterwards remarks, that these oval bodies might be the same with the serpentine, if we suppose them rolled up in a spiral manner.  But still, how is it possible to conceive that an animal, with its body in this restrained posture, should be able to move without extending itself?  I, therefore, maintain, that these oval bodies were only the organic particles separated from their threads or tails, and that the serpentine bodies were the same particles which had not yet been deprived of these appendages, as I have often remarked in other seminal fluids.

 

            Besides, Leeuwenhoek, who believed all these moving bodies to be real animals, who established a system upon that foundation, and who affirmed, that spermatic animalcules were transformed into men and other animals, now suspected them to be only natural machines, or moving organic particles.  He never entertained a doubt, [226] but that these animalcules contained the large animal in miniature.  He remarks,* “Progeneratio animalis ex animalcule in semnibus masculinis omni exceptione major est; nam, estiamsi in animalcule ex semine masculo, unde ortum est, figuram animalis conspicere nequemus, attamen fatis superque certi esse possumus figuram animalis ex qua qnimal ortum est, in animalcule quod in femine masculo reperitur, conclusam jacere sive esse:  Et quanquam mihi saepius, conspectus animalcules in femine masculo animalis, imaginatus fuerim me posse dicere, en libi caput, en ibi humeros, en ibi femora; attamen cum ne minima quidem certitudine de iis judicium ferre potuerim, hucusque certi quid statuere supersedeo, donec tale animal, cujus semina mascula tam magna erunt, ut in iis figuram creaturae ex qua provenit agnoscere queam, invenire fecunda nobis concedat fortuna.”  This opportunity, so much desired by Leeuwenhoek, happily occurred to Mr Needham.  The spermatic animals of the calmar are three or four lines in length, and are visible without the assistance of the microscope.  Their whole parts and organization are easily perceived.  But they are by no means small calmars, as Leeuwenhoek imagined.  They are not even animated, though they have motion, but are only machines, [227], which ought to be regarded as the first union of the organic particles.

 

            Though Leeuwenhoek had not this opportunity of undeceiving himself, he had, however, observed other appearances which ought to have had this effect.  He had remarked, for example, that the spermatic animals of the dog,* often changed their figure, especially when the fluid was nearly evaporated; that, when dead, they had an opening in the head, which did not appear when they were alive; and that the head was full and round, during the life of the pretended animal, and flat and sunk after its death; These circumstances should have led him to hesitate concerning the real animation of these bodies, and to think that the phaenomena corresponded more with a machine which emptied itself, like that of the calmar, than with the properties of an animal. 

 

            I have said that the motion of these moving bodies, these organic particles, is not similar to the motion of animals, and that there is no intervals in their movements.  Leeuwenhoek, in tom. 1. p. 168. makes precisely the same remark:  “Quotiescunque,” says he, “animalcula in semine masculo animalium fuerium contemplatus, attamen illa se unquam ad quietem contulisse, me nunquam vidisse, mihi  dicendum est, si modo sat fluidae superesset materiae in qua sese commode movere poterant; at eadem in con- [228] tinuo manent motu, et tempore quo ipsis moriendum approprinquante, motus magis magifque deficit, usquedum nullus prorftus motus in illis agnoscendus sit.”  It is difficult to conceive, that animals should exist, which, from the moment of their birth to their dissolution, should continue to move rapidly, without the smallest interval of repose; or to imagine that the spermatic animals of the dog, which Leeuwenhoek perceived to be as active on the seventh day as the moment they proceeded from the body of the dog, should be able, during all this time, to move with a celerity which no animal on earth could persist in for a single hour, especially when the resistence [sic] arising from the density and tenacity of the fluid is taken into consideration.  This species of continued motion, on the contrary, has an exact correspondence to the nature of the organic particles, which, like artificial machines, produce their effects by a continued operation, and stop immediately after the end is accomplished.

 

            In the numerous experiments made by Leeuwenhoek, he doubtless observed spermatic animals without tails.  He even mentions them in some places, and endeavours to explain the phaenomenon.  For example, speaking of the semen of the cod, he says,* “Ubi vero ad lactium accederem observationem, in iis partibus quas animalcula esse censebam, neque vitam nequ [229] caudam dignoscere potui; cujus rei rationem esse existimabam, quod quamdiu animalcula natando loca sua perfect mutare non possunt, tam diu etiam cauda concinne circa corpus maneat ordinate, quodque ido singular animalcula rotundum repraesentent corpusculum.”  It would have been more simple, and more agreeable to truth, to have said, that the spermatic animals of this fish sometimes have tails, and sometimes have none, than to suppose that the tails were so exactly wound round their bodies as to give them a spherical figure.  One would be apt to think, that Leeuwenhoek had never fixed his eye upon, or described any moving but those which had tails; he has given figures of none that wanted tails, because, though they moved, he did not regard them as animals.  This is the reason why all Leeuwenhoek’s figures of spermatic animals are very similar, and all drawn with tails.  When they appeared in any other form, he thought they were imperfect, or rather that they were dead.  Besides, it is apparent from my experiments, that, instead of unfolding their tails, wherever they are placed in circumstances proper for swimming, as Leeuwenhoek insists, these pretended animals gradually lose their tails, in proportion to the rapidity of their motions, till, at last, these tails, which are bodies foreign to the animalcules, or threads which they drag after them, totally disappear.  [230]

           

            Leeuwenhoek, speaking of the spermatic animals of man,* says “Aliquando etiam animadverti inter animalcula particulas quasdam minores et subrotundas; cum vero se ea aliquoties eo modo oculis meis exhibuerint, ut mihi imaginarer eas exiguis instructas esse caudis, cogitare coepi anon hae forte particulae forent animalcula recens nata; certum enim mihi est ea etiam animalcula per generationem provenire, vel ex mole minuscule ad adultam procedere quantitatem:  Et quis scit anon ea animalcula, ubi moriuntur, aliorum, animalculorum nutritioni atque augmini inserviant!”  It appears from this passage, that Leeuwenhoek had seen, in the human semen, animalcules without tails; and that he is obliged to suppose them to be recently born, which is directly the reverse of what I have observed; for the moving bodies are never larger than when they separate from the filaments, which is the period that their motion begins:  But, as soon as they are fully disengaged from the mucilage, they become smaller, and continue to diminish till their motion entirely ceases.  With regard to the generation of these animals, which Leeuwenhoek imagines to be certain, no vestige of copulations has been discerned by the most acute observers.  It is purely a random assertion, as may be easily proved from his own experiments.  He remarks, for example, with [231] great propriety, that the milt of the cod* is gradually filled with seminal liquor; and that, after the fish has spent this liquor, the milt dries, and leaves only a flaccid membrane, entirely destitute of every kind of fluid.  “Eo tempore,” says he, “quo asellus major lactes suos emisit, rugae illae, seu tortiles lactium partes, usque adeo contrahuntur, ut nihil praeter pelliculas seu membranes esse videantur.”  How should this dry membrane, which contains neither seminal liquor nor animalcules, produces animalcules of the same species next season?  If they were produced by a regular generation, such a long interruption could not take place, which in most fishes, continues a whole year.  To remove this difficulty, he afterwards remarks:  “Necessario statuendum erit, ut asellus major semen suum emiserit, in lactibus etiamnum multum materiae seminalis gigendis animalcules aptae remansisse, ex qua material plura oportet provenire animalcula seminalia quam anno proxime elapso emissa fuerant.”  This supposition, that part of the seminal liquor remains in the milt for the production of spermatic animals the following year, is perfectly gratuitous, and contrary to observation; for the milt, during this interval, is nothing but a thin dry membrane.  But how will he explain a phaenomenon that takes place in some fishes, and particularly in the calmar, whose seminal liquors are not only renewed every year, but even the [232] membranes which contain them.  Here neither the milt nor the seminal liquor are preserved till the succeeding year; and, of course, their regular reproduction cannot be ascribed to generation.  It is, therefore, apparent, that these pretended spermatic animals are not multiplied, like other animals, by generation; and this circumstance alone would entitle us to conclude, that the moving particles in the seminal fluid are not real animals.  Leeuwenhoek, though he tells us, in the passage above quoted, that the spermatic animals are certainly propagated by generation, acknowledges, however, in another place,* that the manner in which these spermatic animals are produced, is exceedingly obscure, and that he leaves to others the farther elucidation of this subject.  “Persuadebam mihi,” says he, speaking of the spermatic animals of the dormouse, “haecce animalcula ovibus prognasci, quia diversa in orbem jacentia et in semet convolute videbam; sed unde, quaeso, primam illorum originem derivabimus! An animo nostro concipiemus horum animalculorum semen jam procreatum esse in ipsa generatione, hocque semen tam diu in testiculis hominum hearer, usquedum ad annum aetatis decimum-quartum vel decimum-quintum aut sextum pervenerint, eademque animalcula tum demum vita donari, vel in justam staturam excrevisse, illoque temporis articulo generandi maturitatem adesse!  Sed haec [233] lampada aliis trado.”  It is, perhaps, unnecessary to make many remarks on what Leeuwenhoek has here advanced.  He saw, in the semen of the dormouse, spermatic animals which were round and without tails; in semet convolute, says he, because he always supposes that they ought to have tails.  He was formerly certain that these animals were propagated by generation:  Here he seems to be convinced  of the reverse.  But, when he learned, that the vine-fretters (pucerons) were propagated without copulation,* he laid hold of this idea, in order to explain the generation of spermatic animals.  “Quemadmodum,” says he, “animalcula hace quae pediculorum antea nominee disignavimus (the pucerons) dum adhuc in utero materno latent, jam praedita sunt material seminali ex qua ejusdem generic proditura sunt animalcula, pari ratione cogitare licet animalcula in seminibus masculinis ex animalium testiculis non migrare, seu ejici, quin post se relinquant minuta animalcula, aut saltem materiam seminalem ex qua iterum alia ejusdem generic animalcula proventura sunt, idque absque coitu, eadem ratione qua supradicta animalcula generari observavimus.”  This supposition is not more satisfactory than the preceding; for, by thus comparing the generation of spermatic animalcules with that of the vine-fretter, we discover not the reason why they are never seen in [234] the human semen till the age of 14 or 15; nor do we learn whence they proceed, or how they are yearly renewed in fishes, &c.  Notwithstanding all the efforts of Leeuwenhoek to establish the generation of spermatic animals, he leaves the subject in the greatest obscurity, where it probably would have for ever remained, if we had not discovered, by the preceding experiments, that they are not animals, but organic moving particles, contained originally in the food, and found in vast numbers in the seminal liquors of animals, which are the most pure and most organic extracts derived from the food.

 

            Leeuwenhoek acknowledges, that he did not always find animalcules in the male semen; for example, in that of the cock, which he often examined, he never but once saw the eel-like animalcules: And, some years after, he could not discover these eels,* but found animalcules with a large head and a tail, which his drawer could not perceive.  He likewise remarks, that, during one season, he could not discover living animals in the seminal fluid of the cod.+  All these disappointments proceeded from this circumstance, that, though he saw moving globules, he was unwilling to acknowledge them to be animals, unless they had tails, though it is in the form of globules that they most generally appear, either in seminal fluids, or in infusions [235] of animal and vegetables [sic] substances.  In the same place, he remarks, that, though he had often distinctly seen the spermatic animals of the cod, he was never able to make his drawer perceive them:  “Non solum,” says he, “ob eximam eorum exilitatem, sed etiam quod eorum corpora adeo essent fagilia, ut corpuscular passim dirumperentur; unde factum suit ut nonnisi raro, nec fine attentissima observatione, animaadverterem particulas planas atque ovorum in morem longas, in quibus ex parte caudas dignoscere licebat; particulas has oviformes existimavi animalcula esse dirupta, quod particulae hae diruptae quadruple fere viderentur majores coporibus animalculorum vivorum.”  When an animal, whatever be its species, dies, it does not suddenly change its form; from being long like a thread, it does not become round like a bullet; neither does it become four times as large after death as before it.  Not a single article of what is advanced by Leeuwenhoek, in this passage, has the smallest correspondence to the nature of an animal; but, on the contrary, the whole agrees with a species of machines which, like those of the calmar, burst and empty themselves, after having performed their functions.  To pursue this observation a little further:  He tells us, that he has seen the spermatic animals of the cod under different forms, “Multa apparebant animalcula sphaeram pellucidam repraesentantia, and of different sizes,” “Haec [236] animalcula minori videbantur mole, quam ubi eadem antehac in tubo vitreo rotundo examinaveram.”  This is an evident proof, that there is nothing like a uniform and invariable species in these animalcules, and, consequently, that they are not animals, but only organic moving particles, which, by their different combinations, assume various figures and sizes.  Of these organic particles, vast numbers appear in the extract and in the residue of our food.  The matter which adheres to the teeth, and which, in healthy persons, has the same smell with the seminal fluid, is only a residue of our food.  In it we accordingly find a great quantity of these pretended animals, some of which have tails, and resemble those of the seminal fluid.  Mr Baker has given figures of four species of them, which are all a kind of cylinders, ovals, or globules, some of them having tails, and others not.  But, after the strictest examination, I am persuaded, that none of them are real animals, and that they are only, like those in the semen, the organic living particles of the food appearing under different forms.  Leeuwenhoek, who knew not how to account for these pretended animals in the matter adhering to the teeth, supposes them to proceed from certain species of food, as cheese, in which they previously existed; but they are found among the teeth of every person, whatever kind of food be eaten; and, besides, they have no resemblance to mites, [237] or other animalcules which appear in corrupted cheese.  In another place, he tells us that these teeth-animals proceed from the cistern-water which we drink, because he observed similar animals in rain-water, especially when it had stagnated upon leaden roofs.  But, when we give the history of microscopic animals, we shall demonstrate, that most of those found in rain-water are only organic moving particles, which divide, unite, change their size and figure, and, in a word, which can be made to move or to rest, to live or die, as often as we please.

 

            Most seminal fluids spontaneously dilute, or become more liquid, when exposed to the air, or to a certain degree of cold, than when they issue from the body.  But they thicken upon the application of a moderate degree of heat.  I exposed some of these fluids to a degree of cold equal to that of water just beginning to freeze; but the pretended animalcules suffered not the least injury from it.  They moved with equal activity, and during the same length of time, as those to which no cold had been had been applied.  But those which were exposed to a small degree of heat, soon ceased to move, because the liquor thickened.  If those moving bodies were animals, they differed in their nature and constitution from all others, to whom a moderate degree of heat communicates force and motion, and upon whose bodies cold has the very opposite effects.  [238]

 

            Before leaving this subject, upon which I have, perhaps, dwelt too long, I must still add another remark, which may lead to some useful conclusions.  These pretended spermatic animals, which are nothing but organic living particles of food, exist, not only in the seminal fluids of both sexes, and in the remnants of food that adhere to the teeth, but likewise in the chyle and in the excrements.  Leeuwenhoek, having met with them in the excrements of frogos, and of other animals which he dissected, was at first greatly surprised; and, not being able to conjecture from whence animals could proceed so similar to those in the seminal liquor he had just been examining, he accuses his own want of dexterity, and supposes, that, in dissecting the animal, he had inadvertantly opened the seminal vessels, and that the semen had in this manner been mixed with the faeces. But, having afterwards observed the same phaenomenon in the faeces of other animals, and even in his own, he was then totally non-plussed.  It is worthy of remark, that Leeuwenhoek never found animalcules in his own faeces, but when they were liquid.  Whenever his stomach was out of order, and his belly was loose, the animalcules appeared; but, when his food was properly concocted, and his faeces were hard, not a single animalcule was to be found, although he diluted the faeces with water.  These facts seem perfectly to coincide [239] with what we formerly advanced; for, when the stomach and intestines properly perform their functions, the faeces are only the gross dregs of the aliment, and all the nourishing and organic particles are absorbed by the lacteal vessels:  In this case, we cannot expect to find organic particles in the faeces, which are solely composed of the useless and inert part of our food.  But, when the stomach and intestines, from any indisposition, allow the food to pass without being properly digested, then the organic particles mix with the faeces; and, when examined with the microscope, we discover them in the form of living organic bodies.  Hence we may conclude, that people who are troubled with looseness should have less seminal liquor, and be less fitted for the purposes of generation, than those of a contrary habit of body.

 

            I have all along supposed that the female funished a fluid equally necessary to generation as that of the male.  In the first chapter, I endeavoured to prove, that every organized body contains living organic particles; and, in Chap. II. and III. that nutrition and reproduction are effects of the same cause; that nutrition is performed by absorption, or an intimate penetration of organic particles through all parts of the body; and that reproduction is effected by the superplus of these same organic particles, collected from every part of the body, and deposited in reservoirs destined for that purpose.  In [240] Chap. IV. I have shown how this theory applies to the generation of man, and other animals which have different sexes.  Females being organized bodies, as well as males, they must also have some reservoirs for the reception of the surplus of organic particles returned from all parts of their bodies.  This surplus, as it is extracted from every part of the body, must appear in the form of a fluid; and it is this fluid to which I have given the appellation of the female semen.

 

            This fluid is not inert, as Aristotle pretends, but prolific, and equally essential to generation as the semen of the male.  It contains particles distinctive of the female sex, as that of the other sex contains particles proper for the constitution of male organs; and each of them contain all the organic particles which may be regarded as common to both sexes: And hence, from a mixture of the two, the son may resemble his mother, and the daughter her father.  Hippocrates maintains, that the semen consists of two fluids, one strong, which produces males, and the other weak, which produces females.  But, as the seminal fluid is extracted from every part of the body, it is impossible to conceive how the body of a female should produce particles proper for the formation of male organs.

 

            This liquor must enter, by some way or other, into the uterus of viviparous animals; and, in oviparous animals, it must be absorbed by the [241] eggs, which may be regarded as portable matrixes.  Each of these matrixes, or eggs, contains a small drop of the female fluid, in that part which is called the cicatrice.  This prolific drop, when the female has had no communication with the male, assumes, as Malpighius observes, the form of a mole or inorganic mass; but, when it is penetrated by the semen of the male, it produces a foetus, which is nourished and brought to perfection by the juices of the egg.

 

            Eggs, therefore, instead of being common to all females, are only instruments employed by nature for supplying the place of uteri in those animals which are deprived of this organ.  Instead of being active and essential to the first impregnation, eggs are only passive or accidental parts, destined for the nourishment of the foetus already formed in a particular part of this matrix by the mixture of the male and female semen.  Instead of existing from the creation, and each including within itself an infinity of males and females, eggs, on the contrary, are bodies composed of a superfluous part of the food, which is more gross, and less organic, than that of which the seminal fluid consists.  The egg, in oviparous females, answers the same purposes as the uterus and menstrual flux in the viviparous.

 

            To evince that eggs are only destined by nature to supply the place of an uterus in such ani- [242] mals as are deprived of this organ, we have only to consider, that females produce eggs independent of the male.  The uterus, in viviparous animals, is a part peculiar to the female sex; in the same manner, female fowls, who want this organ, have the defect amply supplied by the successive production of eggs, which necessarily exist in these females, independent of all communication with the male.  To pretend that the foetus pre-existed in the egg, and that eggs are contained, ad infinitum, within each other, is equally ridiculous as to maintain that the foetus pre-existed in the uterus, and that the uterus of the first female contained all the uteri that ever were or will be produced.

 

            Anatomists have applied the term egg to things of very opposite natures.  Harvey, in his aphorism, Omnia ex ovo, by the word egg, when applied to oviparous animals, means only the bag which includes the foetus and all its appendages.  He imagined that he perceived the formation of this egg or bag immediately after the junction of the male and female. But this egg proceeded not from the ovarium of the female:  He even asserts, that he could not distinguish the smallest alteration in the ovarium.  It is apparent, that there is not here the most distant analogy to what is commonly understood by the word egg, unless, perhaps, the figure of the bag might have some faint resemblance to that of an egg.  Harvey, though he dissected [243] many viviparous females, never could perceive any change in their ovaria:  He even regards them as glands totally unconnected with the purposes of generation,* though, as we have seen, they undergo very considerable changes.  This able anatomist was deceived by the smallness of the glandular bodies in animals of the deer kind, to which his researches were principally confined.  Conradus Peyerus, who made many observations on the testicles of female deers, remarks, “Exigui quidem sunt damarum testiculi, sed post coitum foecundum, in alterutro eorum, papilla, sive tuberculum fibrosum, semper succrescit; scrosis autem praegnantibus tanta accidit testiculorum mutation, ut mediocem quoque attentionem fugere nequeat.”+  This author ascribes, with propriety, the reason why Harvey observed no changes in the testicles of the deer, to their smallness.  But he is wrong when he tells us, that the changes he had remarked, and which had escaped Harvey, never happened but after impregnation.

 

            Harvey was deceived in several other essential articles.  He insists, that the semen never enters into the uterus, and that it is impossible for it to find admittance; and yet Verheyen found a great quantity of male semen in the uterus of a cow, which he dissected six hours after copulation.3  The celebrated Ruysch informs us, that, [244] in dissecting a woman who had been killed immediately after the act of adultery, he found a considerable quantity of male semen, not only in the uterus, but in the Fallopian tubes.*  Valisnieri likewise assures us, that Fallopius, and other anatomists, had discovered male semen in the uteri of several women.   This point, therefore, though denied by Harvey, is established by the positive testimony of several able anatomists, and particularly by Leeuwenhoek, who found male semen in the uteri of many different species of females.

 

            Harvey mentions an abortion, in the second month, as large as a pigeon’s egg, without any appearance of a foetus.  In this also he must have been deceived; for Ruysch, and several anatomists, maintain, that the foetus is distinguishable by the naked eye, even in the first month of pregnancy.  In the History of the French Academy, we have an account of a foetus compleatly [sic] formed on the twenty-first day after impregnation.  If, to these authorities, we add that of Malpighius, who distinguished the chick in the cicatrice immediately after the egg issued from the body of the hen, we cannot hesitate in pronouncing that the foetus is formed immediately after copulation; and, consequently, no credit is due to what Harvey says concerning the increase of the parts by juxta-position; since these parts exist from the beginning, [245] and gradually expand till the foetus be perfectly mature.

 

            Graaf differs widely from Harvey in his acceptation of the word egg.  He maintains, that the female testicles are real ovaria, and contain eggs similar to those of oviparous animals, only that they are much smaller, and never fall out of the body, nor detach themselves till after impregnation, when they descend from the ovarium into the uterus.  The experiments of Graaf have contributed more to the belief of the existence of eggs, than those of any other anatomist.  They are, notwithstanding, totally void of foundation; for this celebrated author, in the first place, mistakes the vesicles of the ovarium for eggs, though they are inseparable from the ovarium, form a part of its substance, and are filled with a species of lymph.  2.  He is still more deceived, when he informs us, that the glandular bodies are only the coverings of these eggs or vesicles; for it is certain, from the observation of Malpighius and of Valisnieri, and from my own experiments, that the glandular bodies contain no vesicles.  3.  He is wrong in maintaining that the glandular bodies never appear till after impregnation.  On the contrary, these bodies are uniformly found in all females, after the age of puberty.  4.  He errs in supposing that the globules which he saw in the uterus, and which contained the fetuses, were the very vesicles that had descended from the ovarium into the uterus, [246] and that, he remarks, had become ten times smaller than when they were in the ovarium.  This circumstance alone of their diminished size should have convinced him of his mistake.  5.   He is not less unfortunate in maintaining that the glandular bodies are only the coverings of the fecundated eggs, and that the number of coverings or empty follicles always correspond to the number of foetuses.  This assertion is the reverse of truth; for, on the testicle of all females, we uniformly find a greater number of glandular bodies, or cicatrices, than of foetuses actually produced; and they even appear in those which have never brought forth.  To this we may add, that neither he, Verheyen, nor any other person, ever saw the egg in this pretended covering, or in its follicle, though they have thought proper to rest their system upon that supposition.

 

            Malpighius, who distinguished the growth of the glandular bodies in the female testicle, was deceived when he imagined that he once or twice discovered the egg in their cavities; for this cavity contains only a fluid; besides, after numberless experiments, no man has ever been able to discover any thing that had the most distant resemblance to an egg.

 

            Valisnieri, who is never deceived with regard to facts, is wrong in maintaining that the egg must exist in the glandular body, though neither [247] he, nor any man else, was ever able to discover it.

 

            Let us now attend to what may be esteemed the real discoveries of these anatomists.  Graaf was the first who discovered that the testicles of females suffered any change; and he was right in maintaining that they were parts essentially necessary to generation.  Malpighius demonstrated, that the glandular bodies gradually grew to maturity, and that, immediately after, they were obliterated, and left behind them only a slight cicatrice.  Valisnieri illustrated this subject still farther.  He discovered that these glandular bodies were found in the testicles of all females; that they were considerably augmented in the season of love; that they increased at the expence of the lymphatic vesicles of the testicle; and that, during the time of their maturity, they were hollow and full of liquor.  These are all the truths we have learned concerning the pretended ovaria and eggs of viviparous animals: What conclusions are we to draw from them?  Two things appear evident:  The one, that no eggs exist in the testicles of females; the other, that there is a fluid both in the vesicles of the testicle, and in the cavity of the glandular bodies; and we have demonstrated, in the preceding experiments, that this last fluid is the true female semen, because it contains, like that of the male, spermatic animals, or rather organic particles in motion.  [248]

 

             The seminal fluid of females, therefore, being thus fully ascertained, after what has been said, we must be satisfied that the seminal fluid in general is the superfluous organic part of our food, which is transmitted from all parts of the body to the testicles and seminal vessels of males, and to the testicles and glandular bodies of females. This liquor, which issues through the nipples of the glandular bodies, perpetually bedews the Fallopian tubes, and may easily find admission into them, either by absorption, or by the small aperture at their extremity, and in this manner may descend into the uterus.  But, on the supposition of the existence of eggs, which are ten or twenty times larger than the aperture of the tubes, it is impossible to conceive the possibility of their being transmitted to the uterus.

 

            The liquor shed by females in the paroxysm of love, which Graaf supposes to proceed from lacunae about the neck of the uterus and the orifice of the urethra, may be a portion of the superfluous fluid that continually distills from glandular bodies upon the Fallopian tubes.  But perhaps this liquor may be a secretion of a different kind, and no way connected with generation.  To decide this question, microscopic observations would be necessary; but all experiments are not permitted even to philosophers.  I am inclined to think, that, in this liquor, the same spermatic animals, or moving bodies, would be found as appear in the fluid of the glandular [249] bodies.  Upon this subject, I might quote the authority of an Italian physician, who had an opportunity of trying this experiment, which is thus related by Valisnieri:*  “Aggiugne il lodata fig.   Bono d’avergli anco veduti (animali spermatici) in questa linfa o fiero, diro cosi voluttuoso, che nel tempo dell’ amorosa zuffa seappa dale femoine libidinose, senza che si potesse sospettare che fossero di que’ del maschio,” &c.  If the fact be genuine, as I have no reason to doubt, it is certain that this liquor is the same with that contained in the glandular bodies, and, of course, that it is a real seminal fluid, which escapes through the lacunae of Graaf, situated about the neck of the uterus.

 

            Hence we may conclude, that the most libidinous females will be the least fruitful, because they throw out of the body that fluid which ought to remain in the uterus for the formation of the foetus.  We likewise learn why common prostitutes seldom conceive; and why women in warm climates, who have more ardent desires than those of colder regions, are less fertile.  But of this we shall afterwards have occasion to treat.

 

            It is natural to imagine that the seminal fluid of either sex should not be fertile, unless when it contains moving bodies.  But this point is still undetermined. The Italian physician, mentioned above, alledges, that he never found spermatic [250] animals in his semen, till he arrived at 40 years, although he was the father of many children, and continued, after the animalcules appeared, to beget more.

           

            The spermatic moving bodies may be regarded as the first assemblages of the organic particles which proceed from all parts of the body; and, when a great number of them unite, they become perceptible by means of the microscope.  But, when the number united is small, the body they form is too minute to be visible, and no motion will appear in the seminal fluid, a case which not unfrequently happens.  But a long train of successive experiments would be necessary to ascertain the causes of the different states in which this fluid appears.

 

            Of one thing I am certain, from repeated trials, that a seminal liquor, though no motion can be perceived when it is first taken from the body, after being three or four days infused in water, produces as great a number of organic moving particles, as another semen, treated in the same manner, which at first contained vast multitudes.  These moving bodies appear likewise in infusions of the blood, of the chyle, of the flesh, and even of the urine, as well as in infusions of all parts of vegetables; and those which appear in all these different substances, seem to have nothing peculiar to them.  They all move and act nearly in the same manner.  If we will have these bodies to be animated, it must be al- [251] lowed, that they are very imperfect, and ought to be regarded only as the rudiments of animals, or rather as bodies composed of particles essential to the existence of animals.  As Nature’s productions are uniform, and advance by imperceptible degrees, there is no improbability in supposing the existence of organized bodies which properly belong not either to the animal or vegetable kingdoms.

 

            However this matter may stand, it is fully ascertained, that all animal and vegetable substances contain an infinite number of living organic particles.  These particles successively assume different forms, and different degrees of activity, according to different circumstances.  They are more abundant in the seminal fluids of both sexes, and in the seeds of plants, than in any other part of the animal or vegetable.  There exists, therefore, in vegetables and animals, a living substance which is common to them both; and this substance is the matter necessary to their nutrition.  The animal is nourished by vegetable or animal substances; and the vegetable is nourished by the same substances in a decomposed state.  This common nutritive substance is always alive and active.  It produces an animal or a vegetable, whenever it finds an internal mould or matrix accommodated to the one or the other, as has already been explained.  But, when this active substance is collected too abundantly in a place where it has an opportunity of [252] uniting, it forms, in the animal body, other living creatures, as the tape-worm, the ascarides, the worms sometimes found in the veins, in the sinuses of the brain, in the liver, &c.  Animals of this kind owe not their existence to the generation of individuals of the same species.  It is, therefore, natural to think, that they are produced by an extravasation of the organic matter, or by an inability of the lacteal vessels to absorb the quantity of it presented to them.  But we shall afterwards have occasion to examine more in detail the nature of these worms, and of other animals which are produced in a similar manner.

 

            When this organic matter, which may be considered as an universal semen, is assembled in great quantities, as in the seminal fluids, and in the mucilaginous part of the infusions of plants, its first effect is to vegetate, or rather to produce vegetating beings.  These zoophytes swell, extend, ramify, and then produce globular, oval, and other small bodies of different figures, all of which enjoy a species of animal life; they have a progressive motion, which is sometimes very rapid, and sometimes more slow.  The globules themselves decompose, change their figure, and become smaller; and, in proportion as they diminish in size, the rapidity of their motion increases.

 

            I have sometimes imagined, that the venom of the viper, and even the poison of enraged ani- [253] mals, might proceed from this active matter being too much exalted.  But I have not yet had leisure for experiments of this kind, nor for ascertaining the nature of different drugs.  All I can say at present is, that infusions of the most active drugs abound with moving bodies, and that they appear sooner in them than in other substances.

 

            Almost all microscopic animals are of the same nature with the moving bodies in the seminal fluids, and in infusions of animal and vegetable substances.  The eels in paste, in vinegar, &c. are all of the same nature, and derived from the same origin.  But the proofs and illustrations relative to this subject, we shall reserve till we give the particular history of microscopic animals.  [254]       

Notes

 

*  tom. 1. p. 51 [back to page 223]

 

*  P. 52 [back to page 224].

 

*  P. 5 [back to page 225].

 

*  Pag. 67 [back to page 227].

 

*  See tom. 1. p. 160 [back to page 228].

 

*  Tom 2. p. 150 [back to page 229].

 

*  Tom. 3. p. 93 [back to page 231].

 

*  Tom. 3. p. 98 [back to page 232].

 

*  Tom. 1. p. 26 [back to page 233].

 

*  See tom. 2. p. 499. et tom. 3. p. 271 [back to page 234].

 

* See tom. 3. p. 370.

+  Tom. 3. p. 306 [back to page 235].

 

*  See Harvey, Exercit. 64. and 65.

+  See Conrad. Peyer. Merycolog.

3.  See Verheyen, sup. anat. tra. 5. cap. 3 [back to page 244].

 

*  See Ruysch Thes. anat. p. 90. tab. VI. fig. 1 [back to page 245].

 

*  Tom. 2. p. 136 [back to page 250].