174 THE PHYSIOLOGY OF REPRODUCTION 



uterus. These movements were repeated at intervals. Moreover, 

 it was found that the sucking action could be induced artificially by 

 stimulating the erectile tissue of the vulva. It is probable, however, 

 that the spermatozoa, after once entering the uterus, proceed to their 

 destination unassisted, and that the direction ' of their movement is 

 determined by the capacity they possess to respond to the stimuli 

 set up by opposing currents. Moreover, pregnancy has been known 

 to follow imperfect coition in man, so that there can be no doubt 

 that under certain circumstances the spermatozoa are capable of 

 passing inward by their own unaided efforts.^ 



Insemination 



The act of copulation results in the introduction of seminal fluid 

 through the generative aperture of the female. The mechanism by 

 which this is effected in the higher animals is described in a future 

 chapter, where the functions of the accessory male organs are dealt 

 with. The introduction of the fluid into the female generative 

 passages is known as insemination (as distinguished from impregna- 

 tion, which is the term used in reference to the female when 

 fertilisation takes place ^). 



It is obvious that in those animals which ovulate spontaneously 

 during the oestrus periods it should be possible to induce pregnancy 

 at such times by the artificial introduction of spermatozoa into the 

 vagina or into the uterus. That this could actually be effected was 

 probably first demonstrated by Spallanzani,^ though there is evidence 

 that the practice of artificial insemination was not unknown to 

 the Arabs many centuries ago.* The following is a description of 

 Spallanzani's original experiment, as quoted from a contemporary 

 English translation : — 



" I chose a bitch spaniel of moderate size which had before had 

 whelps. Suspecting, from certain appearances, that she would soon 

 be in heat, I confined her in an apartment, where she continued a 

 long time, as will be seen below. For greater security, that she 

 might never be let loose, I fed her myself, and kept the key the 

 whole time. On the thirteenth day she began to show evident signs 



' For further information regarding tlie passage and fate of the spermatozoa 

 in the female body, see Kohlbrugge, "Die Verbreitung der Spermatozoviden 

 im Weiblichen Korper, etc.," Arch. f. Entwick., vol. xxxv., 1912. 



2 That is to say, the animal is inseminated when the spermatozoa are intro- 

 duced, and it is impregnated when the ovum becomes fertilised by a sperm. 

 See Heape, " The Artificial Insemination of Mammals," Proc. Roy. Soc, vol. Ixi., 

 1897. 



3 Spallanzani, Dissertations, vol. ii., London, 1784. 



* Gautier, Le Fecondation artificielle, etc., Paris, 1889. 



