192 PHYSIOLOGY CHAP. 



species : Conception, that is to say, fertilisation of the female sexual 

 cell (ovum) by means of the male sexual cell (spermatozoon). The 

 history of the scientific discoveries in regard to this important 

 part of physiology begins with the demonstration that fertilisation 

 cannot take place except by means of a direct action of the 

 sperm on the ovum. Priority in this demonstration belongs to 

 Spallanzani (1786), who, in his celebrated experiments "On Genera- 

 tion," succeeded in fertilising the ovum detached from the body of 

 the frog by placing it in immediate contact with the sperm ex- 

 pressed from the testicles, the vesiculae seminales, and the deferent 

 ducts of the male. The artificial fertilisations of Spallanzani were 

 then repeated with success by Rusconi on the ova of fishes. 

 Spallanzani and Rassi succeeded first in fertilising a bitch by 

 injecting with a syringe the sperm of a dog. Spallanzaui dis- 

 covered that after diluting 3 grms. of sperm with 18 c.c. of water, 

 one drop of this liquid was sufficient to fertilise many ova of 

 the frog. 



An English experimenter, Haighton (1797), tied one of the 

 oviducts of a bitch, and observed that fertilisation did not take 

 place in the corresponding uterine cornu, while it occurred 

 regularly in the opposite one. 



These facts served to overthrow many old theories on fecunda- 

 tion, for example the view that the influence of the whole organism 

 of the male on the female was necessary; and the other, main- 

 tained by Graaf and widely spread among the old physiologists, 

 that the fertilising action of the sperm could be transmitted to a 

 distance by the so-called aura seminalis. 



Definite proof that in the mammals also fecundation is brought 

 about by the immediate contact of the ovum with the spermatozoon 

 was supplied by the experiments of Prevost and I)umas (1824). 

 They demonstrated that filtered sperm is not capable of fertilising 

 because it is deprived of spermatozoa. Bischoff (1844), having 

 killed a bitch a few hours after coitus, recognised the sperm- 

 atic animalculae in the vagina, the uterus, the tubes, and its 

 fimbriae, the peritoneal cavity, and on the external surface of the 

 ovaries. The fact that for fecundation external contact' of the 

 spermatozoon with the ovum is not sufficient, but that mechanical 

 penetration into the middle of it is necessary, either through the 

 so-called micropile or through the supposed pores or canaliculi of 

 the zona pellucida, was demonstrated for the first time by Barry 

 (1843) in the rabbit. Ten years later his observations were con- 

 firmed by Meissner, and by Bischoff, and extended afterwards by 

 many other investigators upon lower animals. 



The morphological process of fertilisation has been the subject 

 in recent times of numerous and ingenious experiments to clear up 

 if possible the most obscure mysteries of reproduction. The 

 inquiries were extended to the infusoria, to the embryonic sac of 



