MAMMALIA. 721 



even where the inguinal passages are much more open than in the 

 human subject. 



(850.) The quantity of the seminal fluid furnished by the 

 testes is very small, as must be evident from the extreme narrow- 

 ness of the duct through which it passes into the urethra. Ne- 

 vertheless, as the impregnation of the female now requires the 

 forcible injection of this fluid, it is absolutely requisite to increase 

 the bulk of the vivifying secretion, in order to enable the muscles 

 that embrace the urethral "tube efficiently to expel it. For this 

 purpose additional glands are given, whereby different fluids are 

 poured into the urethral cavity, apparently for the sole purpose of 

 diluting the spermatic liquor, and thus forming a vehicle for 

 its expulsion. These succenturiate glands, as they are named, 

 are not found in any oviparous animal ; but in the Mammal such 

 is their size and importance, that there may be just reason for 

 supposing them to exercise a more important office than that 

 usually assigned to them by physiologists ; and this supposition 

 seems to obtain additional weight when we consider the great 

 diversity of structure that they exhibit in different quadrupeds. 



(851.) The vesicultE seminales are the first of these accessory 

 secreting organs that require our notice. In Man the seminal 

 vesicles, as they are erroneously termed, resemble two membranous 

 reservoirs, situated beneath the neck of the bladder, and were once 

 supposed to be receptacles for containing the semen. When 

 opened, however, they are found to be composed of the windings 

 of a very sinuous secreting surface ; and, as their excretory ducts 

 open into the urethra in common with the vasa deferentia, they 

 obviously add the fluid that they elaborate to the secretion of the 

 testes. 



But, notwithstanding their apparent importance in the human 

 species, these organs do not exist at all in by far the greater num- 

 ber of CARNIVOUA ; neither are they found in the RUMINANTS, 

 nor in the cetaceous Mammals. 



In other quadrupeds, on the contrary, they are found ; and 

 their proportionate size is extremely remarkable. This is spe- 

 cially the case in the Rodent tribes, and among the INSECTIVORA. 

 In the Hedgehog, for example, their bulk is enormous. In this 

 creature they form two large masses (Jig. 33, A, c, c), each com- 

 posed of four or five bundles of long and tortuous secerning ves- 

 sels folded upon themselves in all directions, and pouring the 



3 A 



