250 THE PHYSIOLOGY OF REPRODUCTION 



On the other hand, the corpora cavernosa and the glans are 

 represented by homologous structures. The clitoris, like the 

 penis, contains very numerous sensory nerve endings ^ and under- 

 goes erection during sexual congress. 



The relation between the clitoris and the uro-genital canal 

 is closer in some Mammals than in others. In some species 

 {e.g. the capybara among the Rodents, and Twpaia among 

 Insectivores) the clitoris is of considerable size, and is grooved 

 along its under surface in relation to the upper wall of the 

 urethra. In other animals {e.g. Arvicoh, Talpa, and Stenops) 

 the groove on the under surface of the elongated clitoris is 

 converted by the coalescence of its margins into a tube, which 



Fig. 64.— Distal end of bull's penis as seen from left side, showing glans and 

 urethral papilla representing vestigial filiform appendage. The prepuce 

 is folded back. About two-thirds natural size. 



constitutes the urethral portion of the uro-genital canal. 

 Further, in the female of the spotted hyena {H. crocuta), the 

 whole of the uro-genital canal, beyond the apertures of the 

 ducts of Barthohni's glands, is prolonged forward to the ex- 

 tremity of the clitoris and terminates in a similar manner 

 to that of the urethra of the male. In this animal, therefore, 

 the vagina is completely absent, the os uteri opening directly 

 into the uro-genital canal, which is elongated and tubular in 

 form as in the male. A somewhat similar condition has been 

 known to occur abnormally in the human female.^ 



1 ■Worthmann,"Beitrage zur Kenntniss der Nervenausbreitung in Clitoris 

 und Vagina," Arch. f. Mikr. Anat., vol. Ixviii. 



2 Watson (M.), " The Homology of tlie Sexual Organs illustrated by Com- 

 parative Anatomy and Pathology," Jour, of Anat. and Phys., vol xiv., 

 1879. 



