4o8 



DISCOVERY REPORTS 



however, circular muscle layers are powerfully developed (Fig. 18 a) ; they are probably 

 continuous with the circular layers within the walls of the uterus, although no sections 

 were taken to prove this point. These strong circular layers are continued up into the 

 limbs of the folds where they form an extremely stout mass of circular muscles within 

 the folds themselves (Fig. 18). Outside the circular muscles is a serous coat, which is 

 also prolonged into the folds and carries blood vessels into them. The papillate ridges 

 of the vaginal wall are continued over the folds longitudinally (Fig. 18). 





;;i y 1* " ^ • .» ' v . ^ 



:'. ■ k •■ ,: -**c 'J /:■-**;■ 



Fig. 17. Transverse section across the 

 smooth part of the vaginal wall in a 

 2.1 m. Fin whale foetus. (At right 

 angles to the long axis of the vagina.) 



a. Longitudinal muscle layer, poorly 

 developed. 



b. Epithelium (intact only between the 

 ridges). 



c. Fibrous corium. 









Fig. 18. Transverse section across one of the folds of the 

 upper part of the vaginal wall in a 2-1 m. Fin whale foetus. 

 (Parallel with the long axis of the vagina.) 



a. Circular muscle layer. b. Epithelium. 



Immediately in front of the external opening of the vagina into the vulva the inner 

 surface of the wall again exhibits a folded arrangement (Fig. iu). These folds are 

 longitudinal and take origin from a sharp constriction which marks off the vagina from 

 the vulva. They are chiefly lateral in position and by their presence form two deep main 

 grooves, with other subsidiary ones, on either side of the posterior part of the vagina, 

 while immediately dorsally and ventrally is a raised area which is not folded and has a 

 plane surface (Fig. n). The lateral longitudinal folds pass forwards along the side walls 

 of the vagina for about a third or less of the length of the smooth part of the passage and 

 diminish anteriorly, merging with the plane surface of the wall, while the grooves 

 caused by their presence widen out and disappear. Sections across these longitudinal 

 folds (Fig. 19) show that they are made up of the fibrous corium of the vagina — the 

 connective tissue fibres being directed upwards into them. Within the grooves the lining 

 columnar epithelium of the vaginal wall is intact. Although the glands are not yet 

 properly developed in the corium the grooves between the glands suggest by their 

 appearance that they are highly glandular in older whales ; indeed, at the summits of the 

 folds the glands can already be seen in section both within the grooves and around the 

 crest of the folds. It is possible that these glands correspond to the glands of Bartolini 

 which occupy a similar position in other mammals. At this terminal part of the vagina 

 occurs the vaginal sphincter muscle already referred to. 



