MITOCHONDRIA IN VERTEBRATE NERVE CELLS l7 



quantitative fluctuations. Mitochondria occur in all parts of 

 the nerve cell, in the axone as well as in the dendrites, for these 

 basic chemical reactions to which I refer are common to the 

 whole protoplasm. Herein the mitochondria diiTer from the 

 Nissl substance, which we must look upon as a more specialized 

 cell organ. While I regret and deplore the absence of experi- 

 mental evidence, I nevertheless feel myself justified in enter- 

 taining, on these grounds, for the time being at least, the hy- 

 pothesis that mitochondria are concerned with the metabohsm 

 of the nerve cell. 



This conception is supported by evidence from analogy con- 

 cerning mitochondria in other than nerve cells. They may almost 

 (but not quite) be regarded as coexistent with protoplasm. They 

 occur, with few exceptions, in the cells of plants (Guilliermond 

 '12, p. 412; Maximow '13, p. 242, and many others) as well 

 as in those of animals. They are transmitted from one gen- 

 eration to another through the medium of the egg, and, in 

 some cases, of the sperm also (Meves '13, p. 225). On cell 

 division, whether it be by mitosis or amitosis, they are dis- 

 tributed in approximately equal amounts to the two daughter 

 cells (Romeis '13, p. 17). Cells in which mitochondria do not 

 occur are less numerous but no less instructive. All at- 

 tempts to demonstrate them in bacteria (Guilliermond '11, 

 p. 200), in the most superficial cells of the epidermis (Firket 

 '11, p. 544) and in the circulating red blood cells of man (Cowdry 

 '14 b, p. 17) have failed. Moreover, GuiUiermond ('12, p. 379) 

 states that he cannot demonstrate mitochondria in the later 

 stages of the life cycle of barley, wheat, maize, bean and pea. 

 Now bacteria are primitive organisms in which the occurrence 

 of a nucleus is disputed, and the epidermal cells and blood cor- 

 puscles are, like the cereals mentioned by Guilliermond, terminal 

 stages in cytomorphosis. We may conclude, therefore, that 

 mitochondria are present in the majority of actively functioning 

 cells, that they decrease progressively with a diminution in cell 

 activities and that they are absent in the most primitive organ- 

 isms. In other words, that, so far as we know, the ground 



THE AMERICAN JOURNAL OF ANATOMY, VOL. 17, NO. 1 



