380 THE MALE KEPKODUCTIVE OKGANS 



in the spermatozoon it forms a very dense compact mass. At the 

 same time the cytoplasm is at first collected at one pole of the 

 spermatid and then elongated to form the long flagellate tail of 

 the spermatozoon. The middle piece of the spermatozoon seems 

 to arise partly from the attraction sphere and partly from the 

 cytoplasm of the spermatid. 



The lumen of the seminiferous tubules is occupied by either 

 the fully formed spermatozoa or by the developing tails of such 

 of them as are still attached to the Sertoli cells, together with a 

 scanty fluid secretion in which they are suspended, and numerous 

 particles of granular debris which result from the degeneration 

 of many spermatids which for some reason fail to develop into 

 spermatozoa. 



TUBULI RECTI 



At the apex of the testicular lobule the tortuous seminiferous 

 tubules pass into the rete testis of the mediastinum. At this 

 point the tubule becomes straight and is abruptly narrowed. Thus 

 the short straight tubules, tubuli recti, are formed. In the 

 straight tubules the stratified epithelium of the tortuous portions 

 is abruptly exchanged for a very low columnar or flattened type 

 of epithelium with which the Sertoli cells of the tortuous tubules 

 seem to be continuous. The straight tubules are very short and 

 are soon transformed into the irregular anastomosing canals of 

 the rete testis. 



EETE TESTIS 



The connective tissue of the mediastinum is permeated by a 

 network of irregular channels of varying diameter which present 

 frequent dilatations and often have the appearance of broad cleft- 

 like spaces. These are the canals of the rete testis which form a 

 dense network of anastomosing channels. On the one hand they 

 receive the straight tubules, and on the other they pass into the 

 ductuli efferentes, which convey the secretion onward to the 

 globus major of the epididymis. 



The canals of the rete testis are lined by cuboidal or flattened 

 epithelium, which rests upon a delicate basement membrane. 

 This in turn is supported by the connective tissue of the medias- 

 tinum. The broad but irregular lumen of the canals is occupied 

 by the secretion from the seminiferous tubules and contains many 

 spermatozoa. 



