GENERATION. 



461 



it apparent that we ought in the present state of 

 our knowledge to be very cautious in making 

 any general conclusion regarding the nature of 

 the spermatic animalcules. It appears to be 

 fully proved that some such animalculae always 

 exist in the seminal fluid of animals when they 

 are fit for propagation ; but it is by no means 

 certain that they belong exclusively to the fluids 

 which are the product of secretion in the tes- 

 ticle, for animalculae very similar to them in 

 general appearance and in motions are to be 

 found in various other fluids and organs of 

 animals. In all those parts of the body in 

 which mucous secretions are accumulated, ani- 

 malculae are formed, and in some of the lower 

 animals the Cercariae of intestinal mucus are 

 hardly to be distinguished from the animal- 

 culae of their seminal fluid. 



Nor is it well ascertained that these animal- 

 cules belong exclusively to the fluid of the tes- 

 ticle, and do not sometimes occur in the secre- 

 tions of other parts of the generative organs. 

 They exist no doubt frequently in the seminal 

 fluid of the testicle, but some recent observa- 

 tions seem to shew that they are frequently 

 imperfect in the fluid of that organ, and that in 

 some animals at least they are not fully formed 

 and do not acquire their powers of active mo- 

 tion till some time after the seminal fluid is 

 secreted, and when it has passed from the tes- 

 ticle into other parts of the generative organs. 

 On this account some hold, and with good 

 reason, that they are to be regarded as the pro- 

 duct of reciprocal changes of the ingredients of 

 the seminal fluid on one another, rather than as 

 secreted along with that fluid directly from the 

 bloodvessels of the testicle, as others have sup- 

 posed. 



In conclusion, we would remark that in 

 regard to the seminal animalculae having both 

 the body and tail, such as those that may be 

 seen in the dog, cat, rabbit, or other quadru- 

 peds, and which were described by the dis- 

 coverers and early observers of the seminal 

 animalculae, no one who has had an oppor- 

 tunity of observing them carefully with a good 

 lens magnifying three or four hundred diame- 

 ters can doubt for a moment that they bear a 

 close resemblance to some of the Infusoria, and 

 that both from their structure and motions they 

 are with as much justice as the Infusoria to be 

 regarded as distinct animal beings. With re- 

 gard to the other kinds above mentioned, or the 

 changes they may undergo in different stages 

 of their existence, farther investigations appear 

 necessary to enable us to form an opinion. 



Although the spermatic animalcules, like 

 other Entozoa, are formed only in living ani- 

 mals and may be regarded as dependent for 

 life on those animals in which they occur, yet 

 they retain their life for a time after they leave 

 the body. Thus the spermatic animalcules of 

 the Polecat, which Prevost and Dumas ob- 

 served with much attention, continued to move 

 for fifteen or twenty minutes on the object- 

 stand of the microscope ; and these experimen- 

 ters state that when the seminal fluid is allowed 

 to remain in the genital organs, the animalcules 



continue to live for fifteen or eighteen hours 

 after the death of the animal. Their motions 

 cease instantly when a strong electric spark is 

 passed through the fluid containing them. 



Immediately after the discovery of the semi- 

 nal animalcules, they were made the subject of 

 very fanciful hypotheses, and were conceived to 

 throw quite a new light upon some of the ob- 

 scure parts of the generative process. To the 

 supporters of the theory of pre-existing germs, 

 their discovery opened up the prospect of being 

 able to trace backwards one link more than had 

 previously been done in the chain of life which 

 connects the parent and offspring. By some 

 they were considered as the cause of sexual en- 

 joyment or venereal propensities. By others, 

 the animalculae were held to be of different 

 sexes, and, accord ing as one or other gained the 

 egg during fecundation, to give rise to a male 

 or female offspring, and thus to determine its 

 sex. They have been supposed by others to 

 form the first rudiments of the foetus or lay 

 the foundation in the germ of the egg from 

 which the offspring is afterwards developed, 

 and fecundation has thus been resolved into 

 the simple passage of a seminal animalcule 

 into the germinal part of the egg; and finally, 

 one or two of the most fanciful of such dream- 

 ing physiologists have (as we had occasion to 

 remark at a former part of our article) not failed 

 to perceive on a sufficiently minute inspection 

 of the animalcule, that it already possessed 

 all the organs belonging to the mature con- 

 dition of the animal in the seminal fluid of 

 which it existed; compressed no doubt into 

 a very small space, but from which it was easy 

 to suppose the offspring to be formed by evo- 

 lution.* 



Such notions require no refutation. Let us 

 rather pass now to the inquiry of how far ob- 

 servation and experiment have tended to throw 

 light upon the essential circumstances upon 

 which the fecundating property of the seminal 

 fluid depends. 



The nature of the change which confers 

 upon the egg the power of production is entirely 

 unknown to us,and we already remarked towards 

 the commencement of this article that this action 

 is to be ranked among those vital operations of 

 the animal economy which are placed beyond 

 the reach of our means of investigation. We 

 should with equal prospect of success proceed 

 to inquire how life originates and is maintained 

 in the parent, as to investigate the secret man- 

 ner of the transmission of the vital spark from 

 the parent to the offspring. The physiologist 

 who would study this subject must therefore 

 limit his inquiries in this as in other departments 

 of his science to the search after those condi- 

 tions or chain of circumstances which appear 

 to be essential to the occurrence of the parti- 

 cular change or phenomenon which is the 

 object of his investigation. 



Our present object, then, is not to investigate 

 the nature of the change by which the living 



* Gaultier, Generation des Homines et des 

 Aniniaux. Paris, 1750. 



