MITOCHONDRIA IX PLAXT AXD ANIMAL CELLS. 



Janus green G differs only in the substitution of a dimethyl 

 group in the place of the diethyl group in the safranin molecule. 

 Janus blue and janus black I were first introduced as vital stains 

 for mitochondria by E. V. Cowdry ('16, p. 431). Janus blue is 

 the trade name for diethylsafranin-B-napthol and janus black I 

 is a mixture of diethylsafraninazodimethylanilin and some other 

 dye of unknown constitution. Diethylsafranin may easily be 

 made from janus green by splitting off the azodimethylanilin 

 group (Cowdry, '14, p. 269). I have applied these dyes to the 

 mitochondria in the cells of the pea radicle and the acinus cells 

 of the pancreas with the following results. 



TABLE III. 



Dye. Cells of Pea Radicle. Acinus Cells of Pancreas. 



Janus green B + Intense + Intense 



Janus green G 



Janus blue + 



Janus black I + 



Diethylsafranin ? ? + faint 



Nilblue B, extra + faint + faint 



It will be seen that the mitochondria in plant cells react to' 

 vital stains in precisely the same way as in animal cells, even to 

 this extraordinarily delicate janus green test. It is very much 

 more difficult, however, to get a good stain in plant cells by 

 reason of their tough, cellulose walls offering an almost insur- 

 mountable barrier against the penetration of the dye; and 

 janus green is at best but a poor penetrator compared with 

 neutral red, methylene blue and others. For this reason the 

 staining of mitochondria is much slower than in animal cells. 

 Great difficulty was also experienced in finding a suitable medium 

 for the examination of the two tissues. At first they were exam- 

 ined, side by side, in weak aqueous solutions of the dyes to which 

 sodium chloride had been added in varying amounts. This 

 proved entirely satisfactory for the pancreas, but failed with the 

 pea, for which a sugar solution was used. Another trouble with 

 the pea, not encountered with the pancreas, is that the cells are 

 cemented closely together and are therefore so very difficult to 

 separate by teasing, that thin sections of the living pea radicle 

 had to be cut with a razor blade. This method also is objection- 



