FEMALE GENITAL SYSTEM: INTERNAL ORGANS 407 



The vagina 

 The vagina (Fig. 12 / 4 ,/ s ) has considerably thicker walls than the uterus and widens 

 rapidly from the os backwards. In the 2-1 m. foetus the vagina was 15-0 cm. in length 

 from the os to the vulva, and 3-5 cm. in its greatest width which occurs in its anterior 

 third. From this region it diminishes slightly to the vulva. 



The vagina may be regarded as consisting of two parts — an anterior part occupying 

 about a quarter of the length of the passage where the walls are thrown into a number of 

 circular folds (Fig. 12/ 4 ), and a posterior part, occupying the remaining three-quarters 

 of its length, where the walls are plane and unfolded (Fig. 12/ 5 ). In the foetus examined 

 the anterior three folds in the wall of the fore part of the vagina projected funnelwise 

 backwards, reducing the cavity to extremely narrow dimensions. The two foremost of 

 the three are very large, but the third is considerably smaller (Fig. 12/ 4 ) ; the fourth is 

 smaller than the three preceding ones and projects forwards funnelwise into the lumen 

 so that its lips touch those of the backwardly projecting funnel in front of it. Two or 

 three other very much smaller folds, of which only the foremost runs completely round 

 the vagina, intervene between the much folded part and the posterior unfolded part of 

 the vagina. 



At least six vaginal folds were thus found. There are individual as well as specific 

 differences in the numbers of folds in the vaginal wall. The following is a selection from 

 the accounts of various authors showing the variations in the numbers of these folds 

 which are of universal occurrence throughout the Cetacea. 



Balaenoptera musculus, 8. Beauregard and Boulart (1882). 



Balaenoptera physalus, 4. Beauregard and Boulart (1882). 



Balaenoptera physalns, 12. Daudt (1898). 



Balaenoptera physalus, 6. Ommanney. 



Delphinapterus lencas, 8. Watson and Young (1879). 



Globicephala melaena, 4. Murie (1873). Another fold also on which the mucosa was 

 uterine. 



Orcella brevirostris, 3-4. Anderson (1878). 



Phocaena phocaena, 9-12. Daudt (1898). 



Ziphius sp., 5. Scott and Parker (1889). 

 The inner surface of the walls of the vagina is made up of a great number of very 

 small anastomosing ridges, which run in a longitudinal direction and are continued over 

 the anterior funnel-shaped folds. In transverse sections across the wall of the vagina 

 (Fig. 17) the ridges are seen to be covered with lateral papillae, giving to the section of 

 the ridge a compound appearance. The lining columnar epithelium is more than one 

 stratum in thickness and appears to have an outer cornified layer. It is found intact 

 only in the depressions between the ridges (Fig. 17 b). At this stage at any rate no 

 glands were seen opening into the vagina. The lining epithelium is based upon a 

 fibrous corium throughout the vagina. In the posterior plane-walled portion the muscle 

 layers are poorly developed (Fig. 17 a), and only a scanty layer of muscle fibres was 

 detected having a longitudinal direction. In the folded section of the vaginal wall, 



