494 V. D. LESPINASSE 



recti along the interlobular septa and immediately beneath the tunica 

 albugenea. They are supported in a meshwork of fibrous reticulum. This 

 meshwork is abundant and tight in some animals and very loose in others. 



The relation of the blood supply is naturally intimate because of their 

 location. The arteries coming through to supply the walls of the sper- 

 matogenic tubules are in close relation to the cells, but they send out a 

 relatively small number of capillaries to them. The individual cell has 

 an eccentrically placed mass of condensed granular cytoplasm containing 

 the nuclei, while the external portion of the cell is extensively vacuolated. 



The extensively vacuolated forms have been considered as old cells, the 

 opposite being youthful forms. The vacuolated spaces may be smooth 

 and regularly circular or they may be long, irregularly shaped with ragged 

 margins. 



Embryonal Origin. It is generally considered that the interstitial cells 

 are formed from Pfliiger's cords. They are present very early in the 

 embryonic life of the individual and by some are considered to determine 

 the development of the male sex, as in the female no similar group of 

 cells is observed. Another idea is that the interstitial cells are simply hypo- 

 developed spermatogenic cells, due either to a general lack of development 

 in the spermatogenic cells as a whole or to pinching off of small fragments 

 of the spermatogenic cells from the general spermatogenic tubule mass 

 to form the interstitial cells. There are three views as to the possible 

 sources of origin for the interstitial cells and each view has its defenders : 

 first, they may be derived from mesenchyme connective tissue cells; sec- 

 ondly, they may develop from Pfliiger cords, or thirdly, they may de- 

 velop from the cells of the spermatogenic tubules. 



In the writer's opinion, the interstitial cells are different from, and 

 have no direct origin from, the spermatogenic cells. 



The facts to maintain this hypothesis are as follows : 



(1) Interstitial cells are formed before the spermatogenic tubules 

 are formed. 



(2) They contain granules which are undoubtedly secretion granules. 



(3) In many persons with pathological testicles, the individual re- 

 tains his sexual characteristics and sexual libido even when all 

 the spermatogenic tubules are lacking. 



Some have believed that the interstitial cells are ordinary connective 

 tissue cells slightly differentiated. The interstitial cells elaborate gran- 

 ules when the embryo is less than 30 mm. long, whereas spermatogenic 

 tubules only begin to manifest themselves approximately at birth. Con- 

 sequently, we know that when the spermatogenic tubules have not as 

 yet been developed, the interstitial gland is already actively functioning. 



Growth. The interstitial cells appear when the embryo is 30 mm. long. 

 At about 120 to 150 mm. the semen bearing co-rds appear and have a 



