Cytomorphosis of Human Testicular Cells 91 



spermatogenesis has generally been looked upon as the result 

 of a concentration or dehydration of the karyoplasm. The 

 electron microscope observations reported here suggest that 

 the process is not as simple as this and that it involves not 

 only profound alterations in the state of dispersion of the 

 nuclear chromatin but, very likely, changes in its chemistry 

 as well. 



Observations on the interstitial cells 



Appearance with the light microscope 



Human interstitial cells occur as groups of elongated, 

 rounded and polyhedral cells of diverse cytological character. 

 The marked differences in their appearance are interpreted by 

 some investigators as representing different phases in the life- 

 cycle of the Leydig cells (Hooker, 1944; Williams, 1950). 

 Since mitotic figures are not observed in mature Leydig cells, 

 it is commonly assumed that they arise by differentiation 

 from spindle cells present in the interstitium, but it remains 

 unsettled as to whether these cells of origin are common 

 connective tissue fibroblasts, or whether they are primitive 

 mesenchymal cells which persist in the adult along the blood 

 vessels and in the lamina propria of the seminiferous tubules. 



When the young interstitial cells are still relatively undif- 

 ferentiated, they have a plump, fusiform shape with a nucleus 

 of infolded or irregular outline, a finely granular chromatin 

 pattern and a small nucleolus. Although they resemble 

 fibroblasts in some respects, they are generally larger, 

 often contain a few lipid droplets (Montagna, 1952) and, 

 with some fixatives, their cytoplasm has a fibrillar texture 

 (Sniffen, 1950). In the course of their metamorphosis into 

 typical Leydig cells, the nucleus is said to become round in 

 contour, eccentric in position and to develop a very distinct 

 nuclear membrane and a large nucleolus. The cell volume 

 increases and the cytoplasmic filaments gradually give way 

 to fine acidophilic granules. In the mature Leydig cell, the 

 cytoplasm becomes increasingly heterogeneous and contains 



