18 E. V. COWDRY 



substance, alone, of the constituents of the cytoplasm is more 

 fundamental. These considerations, coupled with the fact that 

 the mitochondria, wherever they occur, show a certain uni- 

 formity with respect to their morphology and microchemical 

 properties, to my mind, support the view that they play a part 

 in metabolism. 



We do not know in what way they may be associated with 

 metabolic processes in nerve cells, but I believe that Faure- 

 Fremiet, Mayer and Schaeffer ('10, p. 95) have furnished us with 

 a clue. They found, by a detailed study of solubilities, fixatives 

 and stains, that mitochondria are chemically a lipoid albumin 

 complex. This is of course a vague statement, because there 

 are many different sorts of lipoid and a multitude of albumins, 

 but it is nevertheless of importance. The reciprocal relations 

 which I have described between mitochondria and lipoid, the 

 observations of Mawas referred to on page 6, those of M. R. 

 Lewis and W. H. Lewis ('14, p. 332) on tissue cultures, and, 

 above all, the artificial imitation of mitochondria by Lowschin 

 support this view. Lowschin ('13, p. 203) made the so-called 

 ''Myelinformen" of lecithin in water, different salt and albumin 

 solutions (resulting in the formation of lecithalbumin) which 

 showed masses with the same morphology as mitochondria. He 

 observed granules, rods, threads and rows of granules. The 

 granules divided directly and the threads longitudinally. He 

 was able to influence their form by changing the physicochemical 

 properties of their environment. They were soluble in acetic 

 acid and could be fixed by formalin, osmic and chromic acid. 

 In a later paper ('14, p. 269) he discovered that particles of 

 lecithin and cholesterin suspended in glycerin-gelatin, when fixed, 

 stained like mitochondria by the various mitochondrial methods. 

 Kingsbury ('11, p. 316), also, has emphasized the similarity which 

 obtains in the microchemical reactions of mitochondria and lipoid. 

 I find, m.oreover, that janus green, in addition to being a vital 

 dye for mitochondria, stains both lecithin and egg albumin 

 (Kahlbaum), the latter more intensely. 



Notwithstanding the astonishing general similarity of mito- 

 chondria in diverse types of cells slight, but perplexing, varia- 



