INTERSTITIAL CELLS OF URODELE TESTIS 245 



pied by interstitial cells is in a freshly cut testis, particularly 

 in spring, of a yellow or orange color, but this seems due to 

 coloring matter in the lipoids, since no pigment is found after 

 fixation. 



A peculiar network frequently appears, often filling the entire 

 cytoplasm. Its trabeculae and meshes vary greatly in size in 

 different cells. This network has the same staining reactions as 

 the fuchsinophile granules. It appears best, as a rule, after 

 Bensley's Benda's, or Flemming's fixation, but may be seen 

 also after Zenker's with high percentage of acetic acid. Since 

 the individual fuchsinophile granules are not seen in cells when 

 the net is present and since the network is not seen in the cells 

 of the outer part of the tissue block where fixation of granules is 

 most perfect, I have concluded that this feature is a fixation 

 artifact rather than a characteristic cell structure. This is borne 

 out* by preparations with well-fixed peripheral cells. Between 

 such cells and the centrally located ones with networks appear 

 transitional forms. First are cells with only a few of the granules 

 fused, then cells with a partial net and perhaps half of their 

 granules well preserved, and finally cells in which only a very 

 few granules retain their identity. The explanation of this 

 clearly lies in the slow penetration of the osmic acid in the fixers 

 named. This permits the more rapidly penetrating acetic acid 

 to reach the interior of the tissue block first and there act alone 

 upon the fuchsinophile granules, which are particularly sensitive 

 to it. They appear to undergo solution and spread out into the 

 cytoplasm; droplets thus come in contact with adjoining ones, 

 and an irregular net results. The poorly preserved lipoid drop- 

 lets dissolve out in embedding or in staining the sections, and the 

 open meshes of the net result. Particularly coarse trabeculae 

 are seen in regions where the granules are most numerous and fat 

 droplets few and small: in the spring in cells which have become 

 filled with lipoid droplets, among which are but scattered granules, 

 the net produced has correspondingly fine trabeculae and open 

 meshes. 



A similar network has been described by Duesberg ('18). 

 Like myself, he considers it a fixation artifact, but states that it 



