FEMALE GENITAL SYSTEM: EXTERNAL 393 



shown. In the foetus never more than the two pairs above described are seen — the 

 mammary grooves and one other pair lying outside the mammary grooves. 



The genital aperture (Plate III, fig. 2d) is wide and funnel-shaped. It occupies the 

 centre of the vulva and its sides are beset with radiating folds of skin. The urinary opening 

 is small (Plate III, fig. 2 e) and lies under the curve of the finger-like clitoris at the extreme 

 anterior end of the vulva. In the foetus the arrangement of the two apertures was such 

 that the urinary opening could be regarded as situated within the genital aperture, on 

 the anterior wall of it, rather than as forming a separate opening in front of the genital 

 aperture. Thus in the foetus it was really possible to speak of a short urino-genital 

 vestibule. In the adult, however, a fleshy corrugated pad (Plate III, fig. 2/) develops 

 between the two apertures and their relationship changes somewhat, so that the urinary 

 aperture becomes more definitely separated from the genital and comes to lie in front of it. 



This separation of the genital and urinary passages throughout the whole of their 

 length is a primitive feature, of importance in the anatomy of the female urino-genital 

 system of the Cetacea. It is found, according to Weber (1904, p. 253), in some Insecti- 

 vores (Talpa and Sorex), some Prosimiae and, most frequently, in Rodents. Complete 

 separation of the genital and urinary canals takes place in these cases, so that the 

 genital aperture is used only at parturition and coition. In the Rodents, such as the 

 Porcupine and Pedetes, in which this condition occurs, the urinary canal is enclosed by 

 two overlapping folds of the clitoric prepuce which meet ventral to the clitoris and 

 enclose a groove through which the urine is voided to the exterior. In the mole the 

 vagina is closed early in life (Owen, 1868, vol. ill, p. 688) and only the urinary opening 

 is visible from the exterior immediately behind the clitoris. The condition found in the 

 Cetacea is probably derived from one in which, ancestrally, a very short urinary duct 

 existed, such as is found in many Insectivora such as Tupaia. It has possibly arisen 

 as a result of the outgrowth of the fleshy pad between the two openings. 



Within the vulva the most prominent organ is the clitoris (Plate III, fig. 2 a), of 

 which Beauregard and Boulart (1882, p. 180) gave an exact description. The clitoris is 

 embraced by two folds of skin (Plate III, figs. 2 c, 3). They commence in front of the 

 urinary opening and run outwards and forwards on each side of the clitoris, converging 

 to lose themselves anteriorly in the forward extremities of the labia majora (Plate III, 

 fig. 2 c). They represent the labia minora. In the closed condition of the adult vulva the 

 clitoris projects upwards and backwards across the urinary aperture into the genital 

 opening ; but in the extended condition of the vulva it protrudes outwards and back- 

 wards and does not cover the urinary opening. In the foetus the clitoris was a single 

 curved keel-like prominence, triangular in cross-section. Distally it had the form of a 

 tightly-curved finger upon the anterior angle of the vulva with its tip pointing upwards 

 into the vulva (Fig. 11 /). In the adult, however, the clitoris is much shorter relative to 

 its breadth. It has the form of a median finger-like projection emerging at the anterior 

 end of the vulva from between the labia minora. In front of the clitoris a fold of skin 

 (Plate III, fig. 3 a), described by Beauregard and Boulart (1882, p. 180) and Meek (1918), 

 and held by them to represent the praeputium, "covers the clitoris up to about half its 



