132 GEORGE W. CORNER 



rather than the donor of these attentions. The period is not ter- 

 minated by coitus, but continues until the end of three days. 



For the purpose of the present investigation, the condition of 

 oestrus was observed while the animals were alive in the yards of 

 the packinghouse. The sows were marked, and on the day of 

 killing they were traced through the processes of the abattoir and 

 the internal genitalia received from the hands of the eviscerator. 

 The Fallopian tubes were then removed by cutting across the 

 upper portion of the uterine horns, were carried to the laboratory 

 in 0.7 per cent saline solution, and there washed out by inflating 

 them with salt solution through a slit in the wall near the fim- 

 briated extremity. After inflation with the fluid, the tubes were 

 gently 'milked' into a Syracuse dish, and the washings examined 

 with the dissecting microscope. This simple and almost infal- 

 lible method of finding the ova was suggested to us by Professor 

 Evans as an improvement upon Martin Barry's practice of milk- 

 ing the tube without injected fluid ('39). As we have subse- 

 quently found, it had been used by Sobotta (in the rabbit) and 

 no doubt by others as well. 



We found that ovulation occurs on the first or second day of 

 oestrus, and that the stimulus of copulation is not necessary to 

 cause rupture of the follicles. The ovaries of all sows killed 

 during heat contain mature Graafian follicles ready to rupture or 

 just ruptured, in which latter case the ova are in the tubes and 

 may be recovered therefrom for study by the method described 

 below. Little or nothing has been known of the mature ovum 

 of the sow, and we have found no record of any previous observa- 

 tion of the unsegmented ovum from the tube. We measured 

 fourteen fresh tubal ova from nine sows and found the diameter, 

 including the zona pellucida, to vary from 155^ to 165m, the zone 

 being about 10^ in thickness. The ova are plainly visible to the 

 naked eye if placed against a strong light. We have not noticed 

 a radial striation of the zona pellucida either in fresh or fixed 

 ova. The ovum is filled with yolk granules of varying sizes, usually 

 about 3m to 5m in diameter, which are so numerous and so 

 retractile that they quite conceal the nucleus. 



