616 



AVES BIRDS. 



Fi*. 282. 



consideration, has been provided for the purpose of oiling the 

 feathers ; and in water birds the fluid alluded to becomes of very 

 great importance to their welfare, as it causes their plumy covering 

 to repel moisture so efficiently that it is never wet. The gland 

 given for this purpose is called the " uropygium" and is situated 

 upon the back of the os coccygis ; from this source the bird dis- 

 tributes the oily material thus afforded to all parts of its plumage. 



(687.) The male 

 generative organs 

 in Birds are fully 

 as simple in their 

 structure as those 

 of the Reptilia. 

 The testes are 

 two oval bodies 

 (/g. 282, g), in- 

 variably situated 

 in the lumbar re- 

 gion, lying upon 

 the anterior por- 

 tion of the kid- 

 ney. In their 

 intimate structure 

 they consist of 

 contorted and ex- 

 tremely slender 

 tubes, wherein the 

 semen is elabo- 

 rated, contained 

 in a strong cap- 

 sule. The sperm- 

 secreting tubules 

 of each testis 

 terminate in a 

 slightly flexuous 

 vas defer ens (A, 

 i), that opens into 

 the cloaca by a simple orifice (m, m). In most birds it can scarcely 

 be said that a penis exists at all, two simple rudimentary vascular 

 papillae at the termination of the vasa deferentia constituting the 

 entire intromittent apparatus ; so that copulation between the male 



