272 E. V. Cowdry, 



They also stain specifically with diethylsafranin. Diethylsafranin 

 has not, to the best of my knowledge, been employed as a vital stain 

 for mitochondria by any one except Bensley. He found that it stained 

 them specifically in the cells of the pancreas and in chick embryos 

 and I have confirmed his observations. It is possible to observe in 

 the pancreas of the guinea pig, for instance, mitochondria stained 

 with janus green (diethylsafraninazodimethylanilin) lose their color 

 and assume a red coloration. This is accomplished in the more cen- 

 tral parts of the tissue remote from the sides of the cover glass and 

 from the air (vide Michaelis, '99, p. 565). It is due, as both Michaelis 

 and Bensley have pointed out, to a reduction of the dye with a 

 splitting off of the dimethyl anilin group leaving the red diethyl- 

 safranin. So that there can be no question that diethylsafranin stains 

 mitochondria. 



2. Eeaction to fixatives and stains. 



I have demonstrated them in human blood by certain methods 

 in vogue for the study of mitochondria in other tissues. These methods 

 were modified in that imbedding was omitted and that the duration 

 of the various steps was somewhat abbreviated. 



1. Altmann's ('90, p. 27) method. 



2. Bensley's ('11, p. 309) anilin fuchsin methyl green method. 



3. The iron hematoxilin method as employed by Meves ('08, p. 832) 

 after osmic acid fixation. They may be stained, in addition, by 

 Schridde's ('05, p. 695) modification of the Altmann procedure. 



No differences in the number, shape and cytoplasmic arrangement 

 of these bodies could be observed when they were studied (1) unstained 

 in the living cell, (2) stained with janus green and (3) in cells fixed 

 and stained by the methods above mentioned. 



Regaud ('08, p. 662) and others have shown that mitochondria are 

 dissolved when fixed in fluids containing more that an minimum con- 

 centration of acetic acid. These bodies are soluble in acetic acid. 

 I showed this by adding acetic acid to Orth's fluid. The bodies could 

 be readily seen after fixation in unmodified Orth's fluid, but where 

 acetic acid had been added in a concentration of 5°/ they were no 

 longer visible, i. e. they had been dissolved. 



