376 THE GENITOURINARY ORGANS. 



themselves around the ends of Sertoli's columns, a phenomenon 

 which was formerly regarded as representing a copulation of the 

 two elements, although it was clearly understood that no real 

 fusion or interchange of chromatin occurred, but that the close 

 relations of the two were for the purpose of furnishing nourishment 

 to the developing spermatosomes. The whole forms a spermato- 

 blast of von Ebner. Since the spermatids lining the lumen are 

 changed into spermatozoa, and the process is repeated in the cells 

 of the deeper layers as they come to the surface, the result is that 

 the entire column is finally used up. The compensatory elements 

 are supplied by the proliferation of the adjacent spermatogonia. 

 The resulting products again divide, and thus build up an entirely 

 new generation of spermatogenic cells. Hand in hand with these 

 progressive phenomena occurs an extensive destruction of the cells 

 taking part in spermatogenesis. This is shown by the presence of 

 so-called karyolytic figures in the cells, which later suffer complete 

 demolition. 



These developmental changes are represented in the preced- 



Fig. 302. Section of convoluted tubule from rat's testicle (after von Ebner, 

 88). The pyramidal structures are the sustentacular cells, together with spermatids and 

 spermatosomes. Between these are spermatogenic cells, some of which are in process 

 of mitotic division. Below, on the basement membrane and concealing the spermato- 

 gonia, are black points representing fat-globules, a characteristic of the rat's testicle. 

 Fixation with Flemming's fluid. 



ing schematic figure (Fig. 301), and may in part be observed in 

 figure 302. 



In mammalia it has been possible to trace the development 

 of the spermatids into the spermatosomes. These phenomena have 

 been studied and described by numerous writers, and although 

 many conflicting views have been expressed, the essential steps of 

 this process seem quite clearly established. The account here 

 given is based in part on the recent observations of v. Lenhossek 

 and the observations of Benda. Before considering the method of 

 development of the spermatosomes from the spermatids, a few words 

 concerning the structure of the latter may be useful. The sharply 

 outlined spermatid possesses a slightly granular protoplasm and a 

 round or slightly oval nucleus with a delicate chromatic network. 

 In the protoplasm there is found a sharply defined globule, known 

 as the sphere or sphere substance, which lies near the nucleus and 



