CHEMICAL NATURE OF CERTAIN GRANULES 67 



absence of lipoid material so far as the interstitial cells were con- 

 cerned. 



In the pig the general histological characters of the interstitial 

 cells are essentially the same as in the cat; there are, however, 

 some differences which require to be mentioned. The lipoid 

 globules which are so abundant in the cat are virtually absent; 

 consequently the large vacuoles left in the cytoplasm by the solu- 

 tion of these bodies are also absent, and the spongioplasmic frame- 

 work is much tighter. There is, however, an abundance of small 

 vacuoles towards the periphery of the cells. In sections of for- 

 malin material stained by neutral gentian the appearances pre- 

 sented by the granules is about the same as in the cat, except 

 that they are, perhaps, more variable as to size. In preparations 

 stained by iron haematoxylin or by Altmann's acid fuchsin or by 

 Benda's method (after fixation in Flemming's fluid) and in which 

 differentiation has not been carried very far, there is often an 

 embarrassment of granules, and the entire cell-body may appear 

 stuffed with them. A little study shows, however, that in the 

 vicinity of the nucleus small grains predominate, while towards 

 the periphery of the cell larger ones become more numerous; 

 moreover, the small granules often appear arranged in threads. 

 If the differentiation has been well carried out, until the structure 

 of the nucleus is well shown, the small grains give up the stain 

 and the picture does not differ from that exhibited by the prepa- 

 rations stained with neutral gentian, i.e., a number of granules 

 lying in small vacuoles and most numerous at the periphery of 

 the cell (fig. 4). I take it that the small granules arranged in 

 threads are the mitochondrial structures of the cells, and that 

 the larger ones in vacuoles are the granules under discussion. 



This material seemed ideal for applying the test of direct stain- 

 ing of the granules with a specific fat dye such as Sudan III, as 

 there should be absence of the confusion encountered in the cat's 

 testis due to the presence of many globules of lipoids. Thin 

 frozen sections were stained for half an hour in the incubator at 

 37° C. with a saturated solution of Sudan III in 70 per cent alcohol, 

 but on examination proved practically negative. Fatty material 

 within the seminiferous tubules was demonstrated in large amount 



