176 



THE ESSENTIALS OF HISTOLOGY 



division of the spermatogenic cells, and on the discharge of the sperma- 

 to'zoa the process is repeated as before. 



The straight tubules which lead from the convoluted seminiferous 

 tubes into the rete testis (fig. 211) are lined only by a single layer 

 of clear flattened or cubical epithelium. The tubules of the rete also 

 have a simple epithelial lining, but the basement-membrane is here 

 absent, the epithelium being supported directly by the connective 

 tissue of the mediastinum. 



The efferent tubules which pass from the rete to the epididymis, 

 and the tube of the epididymis itself, are lined by columnar ciliated 

 epithelium, the cilia being very long ; these tubes have a considerable 

 amount of plain muscular tissue in their wall. 



FIG. 213. SECTION ACROSS THE COMMENCEMENT OF 

 THE VAS DEFEKENS. 



a, epithelium ; b, mucous membrane ; c, d, e, inner, middle, and 

 outer layers of the muscular coat ; /, bundles of the internal 

 cremaster muscles ; g, section of a blood-vessel. 



The vas deferens (fig. 213) is a thick tube, the wall of which is 

 formed of an outer thick layer of longitudinal bundles of plain muscular 

 tissue ; within this an equally thick layer of circular bundles of the same 

 tissue, and within this again a thin layer of longitudinal muscle. The 

 tube is lined by a mucous membrane, the inner surface of which is 

 covered by columnar non-ciliated epithelium. 



The connective tissue between the tubules of the testis is of very 



