THE SOUTHERN SEA LION 147 



small. It is almost clear and appears to be of a brownish colour. In no. 483 there was 

 a little liquid even in a cornu. The os penis alone of no. 449, a bull of moderate size, 

 was 18 cm. long so that the organ is quite capable of penetrating into the uterus: it was 

 observed that the os uteri of no. 406 exhibited some dark patches as though it had been 

 bruised. 



There is no direct evidence as to whether ovulation is spontaneous or not, but since 

 cows continue to ovulate — outside the breeding season — at a time when no copulation 

 has been observed one must conclude that it is spontaneous. It is a matter for specula- 

 tion whether the energy and enormous weight of the bull may not, in coitu, cause the 

 expulsion of an ovum from a follicle which has already developed marked internal 

 pressure: it has been remarked that the cows are visibly flattened during coitus. 



Note. The left ovary of no. 480 was gorged with blood and one or two partly ripe 

 follicles were filled with it: extravasated blood was also found in the ovaries of nos. 482 

 and 512. 



Vagina. (See PI. XXXII.) Vaginal material from 24 cows was preserved and from this 

 it appears that the cycle is of the usual type in which growth, stratification, destruction 

 and regeneration succeed one another. Neither cornification nor mucification occurs. 



The epithelium of the anoestrous vagina is about 30 /* in height and is composed of two 

 layers of almost cubical epithelium which are divided by a layer which stains less 

 deeply than the rest of the cytoplasm; there is a distinct surface membrane (nos. 450, 

 477 and 465). With the onset of sexual activity proliferation takes place and the middle 

 layers of the resulting compound epithelium become stratified, but the most superficial 

 layers are thrown off (no. 409) and a highly developed condition of stratification is 

 attained thereafter. This stage coincides with the earlier part of oestrus, as is shown by 

 the presence of sperms in some of the corresponding uteri (nos. 482 and 475). The 

 epithelium, which may have attained a height of 150 /*, is now invaded by large numbers 

 of leucocytes, and the outer layers are sloughed off so that the epithelium is reduced to 

 a thickness of three or four cells with a height of 30-35 ^ and an irregular surface 

 (nos. 477, 406 and 483 ; nos. 448 and 458 are also in the oestrous condition). This stage 

 corresponds approximately with the end of oestrus, as is shown by the relevant uterine 

 sections. During post-oestrus the vaginal epithelium again increases in height to a 

 columnar form which has a thickness of 35-45^ and a smooth surface (nos. 492, 489, 

 424, 470, 504, 491, 429, 417, 493 and 430). This columnar stage subsides to a condition 

 closely resembling that described for anoestrus and having a height of 20-30 fi or even 

 less (no. 422 ; nos. 434 and 466 are also in an advanced stage). 



Table VIII is arranged to show, as far as possible, the changes from an anoestrous 

 state through oestrus and post-ovulation to a condition which may be the beginning of 

 a new cycle, resting, or the earliest stage of pregnancy, the last, of course, not being 

 identifiable unless a blastocyst is found. No. 450, the first animal, is in a state of 

 anoestrus, and having regard to the very small size of the ovaries and uterus, and to the 

 entire absence of any trace of a corpus luteum in the former as well as to the small size 

 of even the largest follicle, 0-45 cm., it is reasonable to conclude that this is a virgin. 



4-z 



