MALE ORGANS OF MAMMALS. 641 



CHAPTER XXXVII. 



GENERATIVE ORGANS OF MAMMALIA. 



OUTWARD characters of sex are least marked in Lissenccphala. 

 To distinguish the male from the female Mole, Shrew, Hedgehog, 

 Sloth, Rodent, requires close scrutiny, if not dissection. The 

 male Monotreme is known by his heel-spur ; the female Marsu- 

 pial by her pouch and by her smaller (in Kangaroos much smaller) 

 size. Among Cetacea the tusk distinguishes the male Narwhal, 



and the larger head the male Cachalot : in Seals the canines are 

 ~ 



usually larger in the male. External parts of generation are 

 conspicuous in other Gyrencephala. Besides these, most Rumi- 

 nants have sexual characters in the horns, either by their presence 

 or o-reater size ; the Stallion and Boar have the tusks : these by 

 their greater length distinguish the male Elephant, especially the 

 Indian kind. In the Carnivora the male is the strongest: the 

 Lion is dignified by his grand mane. The larger canines, with 

 greater general size, mark the male sex in most Quadrumana up 

 to and including the Gorilla. Besides some differences in size 



o 



and proportions of body, developments of hair are the outward 

 marks of sex in Bimana. 



A. MALE ORGANS. 



In the Mammalian class the testes attain their most compact 

 form, with most definiteness and finish of parts, in unravelling 

 which anatomy has surpassed itself, chiefly upon the glands as 

 they exist in Man, from which type of testicular structure there 

 is no essential departure in the lower orders. The peritoneum 

 adds a serous layer to the proper sclerous covering of the gland : 

 and when this passes, as in the majority of Mammals, out of the 

 abdomen, it pushes before it another portion of peritoneum, which 

 becomes reflected after the manner of serous membranes, to form 

 the ' tunica vaginalis testis.' This, however, is an accidental 

 adjunct, dependent upon the 'descent of the testis.' The con- 

 stant arid proper covering, ' tunica albuginea,' consists chiefly of 

 the white sclerous tissue : the spermatic vessels ramify therein, 

 especially the veins, so locally as to facilitate the separation of the 

 tunic into an outer dense protective layer, and an inner laxer 

 layer, the seat of the minuter subdivisions of the arteries proceed- 



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