440 E. V. COWDRY 



thing in the theory that mitochondria function in processes of 

 oxidation and reduction it is possible that these two facts may 

 be related. Let us remember also the dyspnoea in acidosis. 

 Moreover, mitochondria respond to a wide range of noxious 

 influences by swelling up before going into solution, which might 

 be due to the effect of increased H ion concentration^'' upon their 

 protein fraction causing it to become hygroscopic and to swell. 

 The affinity of injured cells for basic anilin dyes is probably 

 due to a swing of the reaction in them toward the acid side. 

 The path is now ready for the study of mitochondria in pathol- 

 ogy because Ciaccio ('13), and others, have cleared the way 

 by their careful descriptions of the post-mortem disintegration 

 of mitochondria. It is true that mitochondria are so delicate 

 that they disappear in the pancreas very soon after death, but 

 the same difficulty is not met with in the case of the nervous 

 system and other organs which autolyse more slowly. Key 

 has found mitochondria in spinal ganglion cells 24 hours after 

 death. It is no longer necessary to employ the poorly pene- 

 trating osmic acid containing fixatives because a simple mix- 

 ture of formalin and bichromate, as advised by Regaud, will, 

 with slight modifications (Cowdry '16) answer the purpose much 

 better. While in some cases the usual fixation in formalin, 

 followed by mordanting in bichromate, will fix the mitochondria 

 satisfactorily (i.e., in human brains). 



TECHNIQUE 



Janus green, diethylsafranin and janus blue are the most 

 useful vital stains for mitochondria. They should be applied 

 by injection through the blood vessels in a dilution of about 

 1 : 20,000 of physiological saline. Mitochondria may also be 

 stained by simply immersing the tissue in the dye, but the 

 objection to doing this is that the dyes penetrate very slowly 

 indeed, so that only the most superficial cells are stained and 

 often very unevenly at that. Special difficulties are often met 

 with in invertebrates because janus green is only slightly solu- 

 ble in sea water, and because it precipitates and stains intensely 



"• As suggested to me by Dr. R. R. Bensley. 



