THE REPRODUCTIVE ORGANS 399 



In a few cases the size of the uterus has been still above the average for resting females, 

 but in the majority of cases it has been as low as, if not lower than, the average. This 

 may be seen in Figs. 131 and 132. In the latter figure attention may be drawn to two 

 Fin whales having remarkably large uteri in which involution was evidently not com- 

 plete. In only one case (not included in the above figures) did the uterus appear to 

 have actually been in an early stage of involution. This was in a Blue whale. No. 770, 

 caught at Saldanha Bay on June 21. One cornu of the uterus measured 48 cm. and 

 was thin walled. The other measured only 21 cm. The congestion of the large cornu 

 was evident before it was opened, and the corpus of the uterus, which measured 

 30-0 cm., was also congested. This whale had evidently given birth to a calf quite 

 recently, and it is interesting to note that though involution of the uterus had hardly 

 begun, the corpus luteum had completely changed from the a to the b type. 



Although only this one whale has been met with in which the uterus had not recovered 

 from pregnancy, it must be remembered, in discussing the rate of involution, that the 

 majority of lactating whales killed are those accompanied by large rather than small 

 calves. This is partly because the waters which come within the sphere of the whaling 

 operations appear to be frequented less by the whales which have recently given birth 

 than by those accompanied by large calves, and partly because the whaling regulation 

 in force in the Falkland Island Dependencies, against the killing of mothers with calves, 

 is probably applied more to the small calves than to the large ones which may be very 

 difficult to recognize as such at sea. 



Since it conveys some idea as to whether parturition has occurred recently or not, 

 the involution of the uterus is the most important point for observation so far as this 

 organ is concerned. 



The changes in the size of the uterus are mainly caused by alterations in the blood 

 content of the uterine mucous membrane, and accompanying them are changes in the 

 mucous exudation from the vagina. 



For the histological study of the uterine mucosa small pieces of the uterus were 

 occasionally taken from the cornu about half-way between the uterine end of the 

 Fallopian tube and the junction of the cornua. They were fixed in Bouin or formol- 

 saline, and after sectioning were stained in haematoxylin and eosin. 



The mucous membrane of the uterus is typical, but the ciliated epithelium is rarely 

 intact over the surface. Even in immature whales (Plate XLII, fig. i) it is usually lost 

 except in the openings of the glands. 



In sections of the mucosa no very striking difference is apparent between immature 

 and mature " resting" whales, though the latter may or may not show some congestion. 

 In two Fin whales, Nos. 11 1 and 193, for instance, there was a considerable amount 

 of blood in the capillaries, and in some other whales taken in the same months as these 

 (March and April) some congestion at the edge of the mucosa was found. 



During early pregnancy blood is present in large quantities throughout the mucosa 

 and is especially evident at its edge (Plate XLII, fig. 3). Extravasation of blood takes 

 place, but it is possible that the extra blood supply is kept up until after parturition. 



