CHANGES IN THE OVARY 135 



and if fertilisation is not effected it undergoes degeneration. 

 Heape found that ovulation could not be induced by artificial 

 insemination, nor by any means other than sexual intercourse, 

 and moreover, that intercourse was a sufficient stimulus, even 

 when the progress of the spermatozoa from the vagina into the 

 uterus was artificially stopped, provided that there was no 

 interference with the vascular supply to the ovaries. 



It is stated by Weil '^ that ovulation may take place inde- 

 pendently of coition in rabbits which have given birth to young 

 just previously, and IwanofE,^ in confirmation of this statement, 

 records experiments in which pregnancy was induced in rabbits 

 by the artificial injection of seminal fluid shortly after par- 

 turition. 



In the mouse, ^ the rat,* and the guinea-pig,^ ovulation 

 occurs spontaneously during " heat," and generally, if not 

 invariably, during oestrus. 



In the dog ovulation takes place independently of coition 

 after external bleeding has been going on for some days, or 

 when it is almost or quite over ; in other words, it occurs during 

 oestrus and not during the prooestrum, or at any rate not during 

 the early stages of the prooestrum.* It is probable that the 

 sow also ovulates during oestrus and not during the prooestrum, 

 since it is stated that sows are most successfully served on the 

 second or third day of " heat." Coition, if it occurs earlier, is 

 frequently not followed by conception.' From Hausmann's 

 description it would seem that ovulation does not take place 

 prior to coition, but this statement has not been confirmed.* 



' Weil, " Beitriige zur Kenntniss der Befruchtung und Entwickelung des 

 Kanincheneies," Wien Med. Jahrluch, 1873. 



^ Iwanoff, " La Fonction des Vesicles s^minales et de la Glande pros- 

 tatique," Jour, de Phys. et de Path. Gen., vol. ii., 1900. 



' Sobotta, loc. tit. 



' Tafani, "La F^oondation et la Segmentation stndie^s dans les CEufs des 

 Rattes," Arch. Ital. de Biol., vol. ii., 1889. 



' Rubaschkin, loc. cit. 



" Marshall and Jolly, "Contributions to the Physiology of Mammalian 

 Reproduction: Part I. The (Estrous Cycle in the Dog," Phil. Trans., B., 

 vol. oxcviii., 1905. 



' Wallace (R.), Farm Live Stock of Great Britain, 4th Edition, London, 

 1907. 



' Hausmann, Ueber die Zeugung und Entstehung des wahren weiblichen Eies, 

 &c., Hanover, 1840. 



