QUANTITATIVE STUDIES ON MITOCHONDRIA IN NERVE-CELLS. 



43 



stant an element in their cytoplasm were functionally identical, for although as 

 yet the role played by mitochondria in nerve-cells is unknown there is evidence 

 that they play an important part in other cells. Cowdry (19166) has discussed 

 briefly the literature bearing on the relations of mitochondria to cell metabolism. 

 From such evidence it is safe to assume that they are not an unimportant con- 

 stituent of nerve-cells and that their constancy in amount in the normal cell is 

 definitely associated with its normal activity. 



CONCLUSION. 



There is a constant number of mitochondria per unit volume of cytoplasm 

 in normal nerve-cells of a corresponding type in the mouse. This constant differs 

 for nerve-cells of different types. Sensory and motor cells can not be distinguished 

 on the basis of their mitochondrial content. The significance of constant varia- 

 tions can not be interpreted with our present meager knowledge of the role played 

 by mitochondria, but there is support for the theory that nerve-cells are func- 

 tionally differentiated in the evidence here advanced of their constant difference 

 with respect to the number of mitochondria they contain. 



Finally, I desire to express my cordial thanks to Dr. E. V. Cowdry, who 

 kindly suggested the problem and provided the material for the investigation. 



BALTIMORE, May 31, 1916. 



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