36 LEO LOEB. 



tous state of the stroma are analogous phenomena. We were only 

 rarely able to find mitoses in the interstitial cells. In this respect 

 the latter differed from the tubule cells in which mitoses were 

 quite frequent. There could be found at one end of each testicle 

 a system of branching epithelial ducts, with a narrow lumen. 

 They were lined by a layer of small and densely packed, usually 

 cuboidal or flat epithelial cells, with nuclei which filled the greater 

 part of the cells. In these cells either one or several nucleoli 

 were found. If one nucleolus was present the nucleus resembled 

 that of the tubule cells, except that it was smaller. At other 

 places the lining cells and nucleus were low cylindrical. In the 

 lumen of these ducts not infrequently some invaginations of the 

 epithelium were found. On the one side the ducts formed a 

 union with the tubule of the testicle. Between the two we found 

 transitional structures consisting in part of tubular and in part 

 of duct epithelium. At the other end the ducts entered the fat 

 tissue which surrounded the testicle and made connection with 

 some larger ducts. One change that took place in a number of 

 tubules needs special mention: A few or many, at some places 

 even the majority of the tubule cells underwent certain changes 

 which made them very similar to interstitial cells. They en- 

 larged, became polygonal or somewhat round, and their cyto- 

 plasm stained more strongly with eosin. The cytoplasm became 

 finely vacuolar, at first the periphery and later the greater part 

 of the cell undergoing this change. At the same time the nuc- 

 leoli divided into several particles which were dispersed in the 

 nucleus. The nucleus became a round vesicle which had lost 

 the transparency so characteristic of the nucleus of the tubule 

 cells. Accompanying this change the layer of flat connective 

 tissue cells which separated tubules and interstitial cells disap- 

 peared and at various places interstitial cells adjoined directly 

 the tubule cells, both kinds having become very similar. Such 

 changes seemed to be frequent especially in places where the 

 interstitial cells were swollen and had become finely vacuolar. 

 Three interpretations of this condition suggest themselves: 



i. As a result of their enlargement the interstitial cells push 

 into the tubules, and thus the appearance within the tubules of 

 typical tubule cells adjoining directly cells resembling interstitial 



