MITOCHONDRIA IN NERVE CELLS 45 



cord) and 354 million (in the Purkinje cells of the cerebellum). 

 The levels selected for this investigation and the small pieces of 

 tissue taken from these levels did not include the nuclei exam- 

 ined by Thurlow, so that specific comparisons can not rigidly be 

 made. The magnitudes are seen, however, to be of the same 

 order, except that the upper limit is considerably higher. The 

 number of mitochondria in the large motor cells in the nucleus of 

 the hypoglossus of the white rat was among the lowest determi- 

 nations (187 million) and agrees strikingly with the number here 

 reported in the large motor cells of the spinal cord in the wood- 

 chuck, which is also the lowest determination (186 million). 

 As was found by Thurlow, sensory cells a re not distinguishable 

 as a class from motor cells upon the basis of the number of 

 mitochondria. 



As has been observed before, particularly by E. V. Cowdry, 

 now and then an individual cell will contain many more or, less 

 frequently, distinctly fewer mitochondria than the neighboring 

 cells of the same type, which, being found in the same region of 

 the same section, must have been through exactly the same tech- 

 nique. This possibly indicates that individual cells may be in 

 quite a different condition from the vast majority. Such a situ- 

 ation has been assumed to explain the classical Golgi technique 

 when, as frequently happens, only here and there a cell is picked 

 out and hundreds of surrounding cells are left unstained. In 

 the spinal ganglion the few cells which contained an unusually 

 large number of mitochondria were usually of the smallest type. 



This more or less specific mitochondria-cytoplasmic ratio is 

 another argument against the view maintained by Portier (see 

 discussion in Compt. Rend. Soc. Biol., 1919, T. 82, pp. 244, 309, 

 337) to the effect that mitochondria are organisms living in 

 symbiosis in larger cells. 



The relationship of the mitochondria to the Nissl bodies as it 

 appears in this investigation does not support the idea that the 

 tigroid substance is normally more or less diffused throughout 

 the cytoplasm and that the appearance of rather definite masses 

 is an artifact produced by the reagents. Were this contention 

 correct one would expect more of the mitochondria to be embedded 

 in these precipitation products. 



