CH. LVIIL] 



SPERMATOZOA 



819 



is another structure called an idiosome, containing a number of 

 microsomes. There are also a coloured or chromatoid body whose 

 function is not known, and two centrosomes (see fig. 608). 



The straight tubules consist of basement membrane and lining 

 cubical epithelium only. 



The interstitial connective tissue of the testis is loose, and con- 

 tains numerous lymphatic clefts. Lying in it, accompanying the 

 blood-vessels, are strands of polyhedral epithelial cells, of a yellowish 

 colour (interstitial cells), which frequently contain crystalloid bodies. 



The tubules of the rete testis are lined by cubical epithelium ; the 

 basement membrane is absent. 



The vasa efferentia, coni vasculosi, and epididymis are lined by 

 columnar cells, some of which are ciliated, whilst others are devoid 

 of cilia, and probably possess secretory functions. There is a good 

 deal of muscular tissue in their walls. 



The vas deferens consists of a muscular wall (outer layer longi- 

 tudinal, middle circular, inner longitudinal), lined by a mucous 

 membrane, the inner surface of which is covered by columnar 

 epithelium. 



The vesiculce seminales(fig. 606) are outgrowths of the vasa deferentia. 

 Each is a much convoluted, branched, and sacculated tube of structure 

 similar to that of the vas deferens, 

 except that the wall is thinner, and 

 the lining epithelium is often of 

 transitional character. 



Therms is composed of cavernous 

 tissue covered by skin. The caver- 

 nous tissue is collected into three 

 tracts, the two corpora cavernosa and 

 the corpus spongiosum in the middle 

 line inferiorly. All these are en- 

 closed in a capsule of fibrous and plain 

 muscular tissue; the septa which 

 are continued in from this capsule, 

 form the boundaries of the cavernous 

 venous spaces of the tissue. The 

 arteries run in the septa ; the capil- 

 laries open into the venous spaces. 

 The arteries are often called helicine, 

 as in injected specimens they form twisted loops projecting into the 

 cavernous spaces (see also p. 313). The structure of the urethra and 

 prostate is described on pp. 541-543. 



The Spermatozoa, suspended in a richly albuminous fluid, con- 

 stitute the semen. Each spermatozoon consists of a head, a very 

 short neck, a body, a tail, and an end-piece. The head is of flattened 



-c 



FIG. 610.- Erectile tissue of the human penis, 

 a, Fibrous trabeculse with their ordinary 

 capillaries ; b, section of the venous sinuses ; 

 c, muscular tissue. (Cadiat.) 



