UROGENITAL SYSTEM 145 



mucous membrane. The male organ of reproduction in all 

 mammals up to man possesses similar fibrous corpora caver- 

 nosa abundantly supplied with veins. Moreover, these corpora 

 cavernosa (except in the case of the Marsupials, which differ 

 also through their double penis) are connected with those of 

 the urethra, which in all the higher mammals has been caused 

 by the development of the sinus urogenitalis into a long narrow 

 canal, and with its corpora cavernosa and the glans penis has 

 been most instrumental in the formation of the true penis, 

 whereas the homologous female organ, the clitoris, also provided 

 with corpora cavernosa, is not united with the urethra (except 

 in the Lemur and some of the Lemuridae), nor has it any 

 connection with the urinary discharge. In the bats, carnivora, 

 seals, whales, many rodents and apes, the penis contains inter- 

 nally a supporting bone, but whether this is the case in the 

 anthropoid apes I have been unable to ascertain. 



In most of the rodents the penis is either entirely or parti- 

 ally surrounded by the sphincter ani ; in most of the other 

 mammals it is attached, varying in extent, to the median linea 

 alba, and only in the bats, the apes and man depends from 

 the pubic arch. This cannot, therefore, be reckoned among 

 the distinctive characters of man, but it has been ascertained 

 that the hymen, in its characteristic form, is possessed ex- 

 clusively by the female human subject, the horse, ruminants, 

 carnivora and apes having only what may be called vaginal 

 valves. 



In addition to the organs of excretion and reproduction, the 

 accessory gland organs present many points of similarity and 

 difference. Diisselhorst 1 has made these interesting organs 

 the subject of exhaustive study, and to his work I shall refer 

 as being the most reliable source of information. The Littre 

 urethral glands are present not only in man, in the upper wall 

 of the pars prostatica and in the pars cavernosa of the urethra, 

 but also in the mole and Cheiroptera (Insectivora), in the 

 Leporidae, Muridae and Cavia (Rodentia) and in the Bradypus 

 tridactylus, all Marsupials and Monotremata (Edentata). The 

 Cowperian glands are very widely spread throughout the king- 

 dom of the mammals. In man these aciniform glands are 



1 A. Oppel, loc. cit., vol. iv., 1904. 

 IO 



