THE EGG OF THE DOMESTIC CAT 147 



well marked series of degenerating eggs in its ovaries. This 

 animal had really been intermittently in heat for not much less 

 than a month before she was killed, so the hypothesis seems a 

 very probable one that the eggs observed represent three dis- 

 tinct groups which had reached the limit of their independent 

 ovarian evolution, and had degenerated after waiting in Aain 

 for the appropriate stimulus to their farther development. 



From the facts presented it appears then that at least 70 per 

 cent of a number of cats may ovulate within 50 hours after pair- 

 ing, while, even in much longer periods, that process occurred in 

 none of those not allowed to pair. In addition in the ovaries 

 of animals not allowed to pair there may appear well individual- 

 ized groups of eggs undergoing degeneration in consecutive order. 

 It seems difficult therefore to avoid the conclusion that in general, 

 if not always, in the cat ovulation is dependent upon pairing, 

 although Bonnet ('97) twenty years ago, found a tube egg in an 

 animal which he believed had been confined beyond the possi- 

 bility of impregnation. It is interesting to note that the egg in 

 question was accompanied by two corpuscles which Bonnet 

 supposed to be the two parts of the divided first polar body. The 

 writer finds the division of the first polar body not of very common 

 occurrence, especially in normal eggs. 



One of the most characteristic phenomena related with heat is 

 the unusually abundant blood supply to the uterus and ovaries. 

 Its importance in bringing about ovulation in the rabbit has been 

 shown by Heape ('05) who demonstrated experimentally that the 

 rupture of the follicles will not occur in the usual manner seven 

 to ten hours after pairing, if the excessiv^e blood supply to the 

 ovaries be cut off. In the cat the blood supply seems independent 

 of pairing, i.e., the calibre of the ovarian blood vessels seems about 

 the same during heat whether pairing does or does not occur. 

 But since ovulation does not take place without pairing, it follows 

 either that the estimate is incorrect that in the two cases the blood 

 supply is the same or that there are other factors than blood supply 

 which determine the occurrence of ovulation. Winiwarter and 

 Saintmont ('09) describe a smooth muscle tissue in the theca 

 externa and in the hilum of the ovary which they believe functions 

 in cooperation with blood pressure to rupture the mature follicle. 



