832 MAMMALIA. 



enter the abdomen through an inguinal canal. Still, from their hori- 

 zontal posture, quadrupeds are but little liable to hernia, even where the 

 inguinal passages are much more open than in the human subject. 



(2460.) The quantity of the seminal fluid furnished by the testes is 

 very small, as must be evident from the extreme narrowness of the duct 

 through which it passes into the urethra. Nevertheless, as the impreg- 

 nation 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 dif- 

 ferent 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. 



(2461.) The vesiculce seminales are the first of these accessory se- 

 creting organs that require our notice. In Man, the seminal vesicles, as 

 they are erroneously termed, resemble two membranous reservoirs, situ- 

 ated 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 elabo- 

 rate to the secretion of the testes. 



(2462.) But notwithstanding their apparent importance in the human 

 species, these organs do not exist at all in by far the greater number of 

 Carnivora ; neither are they found in the Ruminants, nor in the ceta- 

 ceous Mammals. 



(2463.) In other quadrupeds, on the contrary, they are found, and 

 their proportionate size is extremely remarkable. This is specially the 

 case in the Rodent tribes and among the Insectivora. In the Hedge- 

 hog, for example, their bulk is enormous. In this creature they form 

 two large masses (fig. 419, A, cc), each composed of four or five bundles 

 of long and tortuous secerning vessels folded upon themselves in all 

 directions, and pouring the product of their secretion into the urethra 

 by two ducts (fig. 419, B, c c), quite distinct from the vasa deferentia. 



(2464.) The prostates are the next succenturiate glands, superadded 

 to the essential generative organs of the placental Mammals ; and so 

 diverse is their structure in different tribes, that it is not always easy to 

 recognize them under the varied forms that they assume. 



(2465.) In Man the prostate is a solid glandular mass, that embraces 



