MITOCHONDRIA IN VERTEBRATE NERVE CELLS 19 



tions do occur in their morphology, resistance to acetic acid and 

 other fixatives and in their staining properties which require 

 to be explained. It is here, I believe, that a knowledge of their 

 constitution helps us, if we postulate slight variations in the 

 relative amounts of lipoid and albumin. Not only the amount 

 but also the properties of mitochondria vary with changes in 

 metabolism. This is true in spermatogenesis where Regaud ('08, 

 p. 661) has detected a progressive increase in the resistance of 

 mitochondria to acetic acid. We may here be dealing with an 

 increased consumption of albumin which would tend to increase 

 the relative amount of lipoid in the mitochondria and in this 

 way increase their resistance to acetic acid. The failure of 

 Jordan ('11, p. 59) and Wildman ('13, p. 427) to observe mito- 

 chondria in the early stages of spermatogenesis may thus be 

 explained because they used fixatives wdth a constant percentage 

 of acetic acid, which perhaps destroyed the mitochondria of low 

 resistance and left the others. It is possible that the formation 

 of lipoid in nerve cells is a process essentially similar but carried 

 to an extreme. In any case the importance of being able to 

 see in the living nerve cell and in many others deposits of the 

 nature of mitochondria, by means of the vital dye janus green 

 can scarcely be overestim.ated. 



The Nissl substance is, in a sense, a more specialized con- 

 stituent of nerve cells. Recent investigation has shown that 

 material very closely allied to it occurs in many types of cells, 

 muscle cells and gland cells for example. Substances of this 

 sort are grouped together and called 'chromidia.' Bensley's 

 demonstration ('11, p. 359) that the chromidial substance is 

 present in the living acinus cells of the pancreas as a continuous 

 deposit which would lead one to believe that Held and others 

 (vide Barker '99, p. 131) may be right in their assertions, which 

 have been too frequently ignored, that the Nissl bodies, instead 

 of being pre-formed elements in the living nerve cell, result from 

 the coagulation (or precipitation) of a substance present in a 

 diffuse, amorphous state. I have recorded some observations 

 which apparently support this notion, so far as the spinal ganglion 

 cells of vertebrates are concerned, my experience with other types 

 of nerve cells being too limited to justify any assertions. 



