THE fe:\iale reproductive organs 



15 



by the hymen. In the guinea-pig a remarkable mechanism 

 exists whereby the vaginal closure membrane is regenerated 

 after each oestrous period. 



The clitoris. The clitoris, situated anteriorly to the vaginal 

 orifice, is a vestigial homologue of the penis. It is composed 

 of connective tissue, surrounded by more or less cornified 

 epithelium. Its homology with the penis is emphasized by the 

 presence (in the human] of erectile tissue; in such lower 



Fig. 8. — Clitoris of Mouse, 



b.e. band of epithelium running down from distal cleft; b.v. blood 

 vessels; u. urethra. 



mammals as the rat and mouse, the urethra, instead of opening 

 to the exterior at the vulva, as is usually the case, traverses the 

 clitoris and emerges at its distal cleft. In certain mammals the 

 clitoris plays a subsidiary part in copulation, but otherwise its 

 value in the reproductive processes appears to be negligible. 



The mammary glands. The mamnicc are usually bilaterally 

 paired organs, consisting of secretory alveoli from which the 

 milk is carried to the exterior by ducts. The ducts are gathered 

 together on the surface into the nipple to facilitate suckling. 

 The exact nature of the secretion which takes place in the 

 mammae is still a subject of controversy, but, whether or not 



