FUNCTIONAL SIGNIFICANCE MITOCHONDRIA 441 



certain proteins in the body fluids. Its toxicity varies in differ- 

 ent cells. Cowdry ('14, p. 279) observed mitochondria stained 

 with janus green in neutrophile leucocytes during amoeboid 

 movement and phagocytosis of minute foreign particles, and 

 Shipley ('16) also studied mitochondria vitally stained with 

 it in actively motile trypanosomes. 



Mitochondria are easily fixed, osmic acid and the mixtures 

 of Altmann ('90, p. 27), Benda ('01, p. 163), Meves COS, p. 832) 

 and Bensley ('11, p. 308) are used frequently. They all con- 

 tain osmic acid. Personally, I have virtually abandoned them 

 because they penetrate so badly. The simple mixtures of for- 

 malin and bichromate (Regaud '10, p. 296) work much better, 

 especially if the formic acid is neutralized with magnesium 

 carbonate, on account of the sensitivity of mitochondria to acids. 

 Moreover, formalin and bichromate often gi\'e good fixation 

 in tough fibrous tumors and in eggs filled with yolk, which are 

 hard to fix in the older fixatives. 



Generally speaking, the mitochondria may be stained by 

 all methods irrespective of the way they have been fixed. The 

 Altmann method and its modifications (Bensley '11, p. 309; 

 Cowdry '16, and others), the Benda ('01, p. 163) method, and 

 iron hematoxylin are most used, though Bensley ('16, p. 47) 

 has just devised a new technique by which the mitochondria 

 are stained with Brazilin. The fuchsin methyl green modifica- 

 tion of Altmann's method gives the most brilliant results, but 

 fades after a year or two. The Benda method is much more 

 permanent. Iron hematoxylin is the most lasting of all, but 

 it is rather less specific. Remarkably good results may be ob- 

 tained with it after formalin bichromate fixation. Since the 

 hematoxylin is very closely bound to the mitochondria a variety 

 of useful counterstains maj^ be used. Thus, toluidin blue or 

 pyronin, or indeed any basic dye, will stain the Nissl bodies 

 in nerve cells beautifully, the mitochondria remaining black. 

 Moreover, sections of the pancreas of the mouse counterstained 

 with safranin and light green will often show the blebs on the 

 mitochondria (which are by some supposed to be forerunners 

 of zymogen) stained red against a green background, the mito- 

 chondria and zymogen granules of course being blue-black. 



