464 



GENERATION. 



semen 1, to egg 1,064,000,000. The addition 

 of a larger quantity of semen, or its remaining 

 longer in contact with the egg, did not, accord- 

 ing to Spallanzani, render the fecundation more 

 complete than the instantaneous contact of the 

 wetted needle's point. Prevost and Dumas 

 state that they found the number of ova fecun- 

 dated by a given quantity of seminal fluid is 

 always below that of the animalcule which they 

 estimated that fluid to contain ; and by a sim- 

 ple process of calculation it was easy to find 

 how many animalculae served each ovum. A 

 certain quantity of seminal fluid, for example, 

 containing 225 animalcules, served to fecun- 

 date 01 only out of 380 ova, to which it was 

 added, so that each ovum required about 3j 

 animalculae for its fecundation, or making 

 allowance for a few of the animalculae which 

 went astray into other ova, it may be stated as 

 three in round numbers. It will be long before 

 the vital processes can be traced with the arith- 

 metical precision displayed in this calculation. 

 Unfortunately for the calculations and even the 

 observations upon which they are founded, one 

 of the authors at a subsequent period published 

 the theory which appears to have prompted 

 them to revive an old and fanciful notion that 

 the animalcule forms the rudiment of the new 

 being. The animalcule, according to this hy- 

 pothesis, makes its way through the stiffjelly 

 surrounding the yolk, gains the centre of the 

 germinal membrane, and esconces itself there 

 in the very centre of that germinal membrane, 

 laying thus the foundation of the primitive 

 streak or the brain and spinal marrow of the 

 foetus : its position (which is always the same) 

 being no doubt determined by the laws of po- 

 larity depending upon the electro-magnetic 

 properties with which, according to equally 

 fanciful theorists, the rudiments of the new 

 being in the egg are endowed. 



Hitherto cold-blooded and oviparous animals 

 only have been alluded to ; but there are not 

 wanting facts which render it highly probable 

 that in viviparous animals also, contact of se- 

 minal fluid with the ovum is the essential part 

 of the fecundating process. Thus, Spallanzani 

 confined a bitch for fourteen days before the 

 arrival of heat, and for twenty-six days after it, 

 so that, during that time, it could have had no 

 connexion with any dog, and at the time of 

 the heat he injected by means of a syringe 

 a quantity of the dog's seminal fluid into the 

 vagina. The bitch brought forth three young 

 exactly at the usual length of time from the 

 period of heat ; an experiment on artificial 

 fecundation, which may in some sort be said 

 to have been performed in the human species 

 is the well-known instance in which John Hun- 

 ter recommended to a man affected with hy- 

 pospadiac malformation of the urethra, which 

 rendered intromission of the seminal fluid 

 impossible, the injection, by means of a sy- 

 ringe, of the seminal fluid into the vagina, 

 an operation which, it is related, was attended 

 with complete success. 



While these facts on the one hand tend to 

 shew that no parts of the genital organs and 

 no other agents are concerned in fecundation 



excepting the seminal fluid and the ova, and 

 on the other hand afford the only positive 

 evidence that can be obtained, that actual con- 

 tact of the one with the other is necessary to 

 induce the change, they have appeared unsa- 

 tisfactory to some physiologisls,who cling to the 

 opinion that, in quadrupeds and birds at least, 

 contact is not necessary, and that fecundation 

 may be effected either by some hidden sym- 

 pathy (or concurrent action taking place in 

 remote parts) between the external and internal 

 organs of the female, or that this change may 

 be operated by some imponderable influence 

 which emanates from the seminal substance, to 

 which the vague name of aura seminalis has 

 been given. 



Course of the seminal fluid within the female 

 organs.' In pursuing our examination of the 

 alleged evidence upon which these and similar 

 hypotheses are founded, it will be necessary 

 to consider in this place another question, 

 respecting which it is difficult in the present 

 state of the inquiry to form a decided opinion, 

 viz. whether, on the supposition of the seminal 

 fluid and ova coming into actual contact, the 

 course of the seminal fluid within the female 

 organs of generation can in any instances be 

 traced, and in what part of these organs it 

 may be supposed to meet with the ova and 

 operate their fecundation. 



In the first place the examples of ovarian 

 conceptions, or rather gestations, have been ad- 

 duced by some as a proof that fecundation 

 necessarily takes place in the ovaries them- 

 selves. But from what was said in a former 

 part of this paper, it will be seen that such a 

 belief is founded on an erroneous view of the 

 nature of these misplaced gestations, as well as 

 of the phenomena which occur in the ovary 

 after conception. There is no reason to believe, 

 we may repeat, that ova found developed in 

 the neighbourhood of the ovary have retained 

 their situation within the Graafian vesicle. On 

 the contrary, they must in all probability have 

 been first discharged from the ovary upon the 

 rupture of the vesicle, and their places occu- 

 pied by corpora lutea; and they may have 

 been fecundated either while loose in the 

 cavity of the peritoneum, or when they have 

 descended some way in the Fallopian tubes, 

 and meeting with the seminal fluid in the 

 course of that tube, have been returned to the 

 vicinity of the ovary by some inverted or un- 

 natural action of the parts.* 



Although, therefore, no very decided opinion 

 respecting the place at which fecundation 

 occurs can be formed from the observation of 

 what are termed ovarian and tubular gesta- 

 tions, we are inclined to think that they shew 



* We need do no more than mention here a view 

 taken by Sir Everard Home of the uses of the 

 corpora lutca, which he holds to be a means of 

 bringing the seminal fluid into contact with the 

 ovum of the Graafian vesicle. This opinion re- 

 quires no remark, as it will be at once perceived 

 that it proceeds on the assumption, shewn to be 

 erroneous in a former part of this paper, that the 

 corpora hitca are formed before the rupture of the 

 vesicles. 



