476 THE SOLIDS. 



the testis ; this expansive property being especially designed 

 to allow of the accumulation of that fluid within the semeni- 

 ferous organ. 



The tubes of the testis contain a vast number of granular 

 cells of various sizes (see Plate LX. jig. 4.), some being 

 several times larger than others, especially in the testis of 

 the adult. Most of these cells contain but a single nucleus ; 

 in others, however, and these the larger cells, there are as 

 many as from two to seven, or even more, distinct nuclei. 

 (See Plate X VI. jig. 1.) 



In the testes of a child, the granular cells present great 

 uniformity of size, and contain, for the most part, but a 

 single nucleus. These cells, as in other tubular glands, form 

 a regular epithelium on the walls of the tubes, the central 

 channel being free ; this arrangement is very evident in the 

 tubes of immature testes ; but far less so in those of the 

 adult organ ; the manipulation to which the latter are subject, 

 when being prepared for microscopical observation, readily 

 displacing the cells. 



It is in these cells, according to the observations of nu- 

 merous observers, that the spermatozoa are developed. For 

 further particulars on the development of the spermatic 

 animalcules, see the article " Semen." 



The tubes of the testes are loosely bound together by 

 bands of fibrous tissue ; it is this tissue which contains the 

 tortuous blood-vessels with which this organ is so copiously 

 supplied. 



That the tubes are not furnished with a distinct external 

 envelope, like those belonging to the kidney, is proved 

 by the fact that they admit readily of being separated from 

 each other, as also of being drawn out to a great length : this 

 last circumstance shows the extent to which the tubes are 

 convoluted, the few anastomoses which take place between 

 them, and their extraordinary elasticity. 



