OVULATION IN MAMMALS, WITH SPECIAL 

 REFERENCE TO THE MOUSE AND RAT. 



WILLIAM B. KIRKHAM. 



Ovulation and its connection, if any, with pairing is a subject 

 that has long engaged the attention of mammalian embryologists. 

 As long ago as 1828 Von Baer made the statement, seemingly 

 based more upon theoretical than upon experimental grounds, 

 that the Graafian follicles of mammals appear not to rupture 

 without pairing, or some analogous stimulation of the female 

 sexual organs. It would seem to be a simple matter to determine 

 in a given mammal whether ovulation was, or was not dependent 

 upon copulation, but the literature of the subject shows long 

 controversies about this point. The matter can best be taken 

 up by considering individually the animals thus far studied. The 

 egg of the dog was carefully investigated by BischofT ('45), who 

 declared that in that animal ovulation is entirely independent 

 of pairing. This observation has since been confirmed by Mar- 

 shall and Jolly ('05), who also found that the bitch has typically 

 two sexual seasons each year. Further confirmation has come 

 from Ancel and Bouin ('08), who, in addition to finding ovulation 

 occurring independently of copulation, discovered that the Graa- 

 fian follicles in the dog rupture in turn. 



Ovulation phenomena in the guinea-pig gave rise to a spirited 

 controversy between Bischoff ('52 and '66), who claimed that 

 the Graafian follicles in that animal ruptured entirely independ- 

 ently of pairing, and Reichert ('61), who declared that ovulation 

 only occurred nine to ten hours after copulation had taken place. 

 In his second paper, replying to Reichert, Bischoff states that 

 he has experimentally demonstrated in dogs, rabbits, guinea- 

 pigs, rats, sheep and swine that follicles mature and rupture with- 

 out relation to pairing, the full data of this work being given in 

 an earlier paper (Bischoff '44). Hensen ('76), in his paper on 

 the early development of the guinea-pig, quotes the opposing 

 views of Bischoff and Reichert, without expressing any opinion 



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