12 E. V. COWDRY 



Mitochondria evidently occur in the spinal ganglion cells of 

 all the forms which I have studied. Their appearance, in speci- 

 mens prepared by Bensley's method, is illustrated by the figures 

 on plates 1 and 2. The figures show the form relations very 

 well, but the color values could not be reproduced on account 

 of the expense. The following description applies only to those 

 parts of the nerve cell found within the spinal ganglion. The 

 peripheral and central processes have, of necessity, been ignored. 



The morphology of the mitochondria is remarkably constant. 

 They vary, in all the animals investigated, from granules (0.25- 

 0.75At, measured in Bensley preparations) to rods (l-2;u) and 

 filaments (2-4^i). Sometimes the granules are arranged in rows. 

 The rods may be dimib-bell shaped or pear-shaped and the 

 filaments occasionally exhibit varicosities. I am unable to dis- 

 tinguish between the spinal ganglion cells of any of these animals 

 on the basis of their mitochondrial content alone. Morpho- 

 logically the mitochondria in the spinal ganglion cells of man 

 are identical with those of the monkey, guinea-pig, white rat, 

 etc. 



The arrangement of mitochondria within the cell is subject 

 to but slight variation. They are generally distributed evenly 

 throughout the cell body. Occasionally they are more numer- 

 ous in the region bordering on the axone hillock. This was 

 observed in the human cell illustrated in figure 1. In the large 

 cells the mitochondria are generally found between the flakes 

 of Nissl substance, while in the small cells they are imbedded in 

 it (figs. 10 a, 12 and 13). In some of the small cells the mito- 

 chondria are confined to the central cytoplasm (fig. 13 b). This 

 condition is rare. They tend to be oriented parallel to the cell 

 wall so that they are placed more or less concentrically about 

 the nucleus. The guinea-pig cell shown in figure 3 illustrates 

 this very nicely. In the medullated processes they are always 

 arranged with their long axes parallel to the length of the process. 

 I have not studied their relations in non-medullated fibers. 



The microchemical reactions of mitochondria are likewise very 

 constant. Janus green and diethylsafranin gave very disap- 

 pointing results, as compared with their action on blood cells, 



