70 R. H. WHITEHEAD 



tions from the chemical processes beheved to occur during fixing 

 and staining — to show that mitochondria chemically considered 

 consist of a combination of proteid with fatty material, which 

 as we have seen, is also the constitution of the granules described 

 in this paper. On the other hand, so far as I am aware, undoubted 

 mitochondria, such as those of the sex cells, have not been stained 

 by a specific fat stain. However that may be, it does not seem 

 possible that the mitochondria of the sex cells of the cat and pig 

 can be identical with the granules in the interstitial cells; for 

 in my paraffin sections of formalin material stained by neutral 

 gentian or Wright's blood stain the granules of the interstitial 

 cells were demonstrated very clearly, while in the seminal epi- 

 thelium absolutely no granules were stained. So that, for the 

 present, one may be permitted to believe with Heidenhain,^ that 

 while Benda has probably brought to light new structures in the 

 case of the mitochondria of sex cells, it is carrying his results too 

 far to identify mitochondria with all cytoplasmic structures 

 which can be stained by his method. 



PLATE 1 



EXPLANATION OF FIGURES 



All the cells were outlined with the camera lucida. Reichert, obj. ^v. 



1 Interstitial cell of cat; neutral gentian. Formalin fixation. 



2 Interstitial cell of cat; Wright's blood stain. Formalin fixation. 



3 Interstitial cell of cat; iron haematoxylin. Formalin fixation. 



4 Interstitial cell of pig; iron haematoxylin. Formalin fixation. 



5 Interstitial cell of pig; Sudan III. Frozen section. 



6 Interstitial cell of pig; Sudan III. Frozen section. 



» M. Heidenhain. Plasma und Zelle, 1907. 



