MITOCHONDRIA IN NERVE CELLS 43 



placed on the form of mitocnondria, at least within certain wide 

 limits and especially in regard to length, for in living cells, as 

 was observed by the Lewises ('15), elongated ones broke up into 

 granules and granules fused into rods and they seemed to readily 

 bend and assume various shapes as they moved about in the 

 cytoplasm. E. V. Cowdry ('18) has pointed out that the form of 

 mitochondria is not correlated with protoplasmic activity or 

 quiescence. 



The long perfusion with oxygenated Locke's solution (the 

 maximum total length being one hour) at body temperature pro- 

 duced no obvious effect on the morphology or distribution of 

 the mitochondria in nerve cells. Autolytic changes after death 

 being comparatively slow in nervous tissue, no change should be 

 ■expected. In fact, E. V. Cowdry ('18, p. 138) makes the state- 

 ment that it is not even necessary to fix nervous tissue while 

 still warm; "six or eight hours after death is often soon enough." 

 It was, however, necessary to rule out this variable. 



In regard to the number of mitochondria, the accompanying 

 table gives the results in a compact form. It is clearly evident 

 that the number of mitochondria, as already noted by Thur- 

 low ('17), in a unit of cytoplasm in the cells of a given nucleus 

 is comparatively uniform. The individual variations between 

 neighboring cells of the same type was, of course, much greater 

 than the averages tabulated. This is due, to a large extent, to 

 the necessity of using such a small surface area — one that will 

 fit in between the nucleus and the periphery of the cell. If the 

 Nissl granules are large the mitochondria are less uniformly dis- 

 tributed in such a small square because in general the mitochon- 

 dria lie between the masses of tigroid substance. The results 

 to be of value must be based upon a sufficiently large number of 

 fields to eliminate this irregularity of distribution. To do this 

 in connection with the motor cells of the ventral horn it was 

 necessary to count the mitochondria in at least twice as many 

 unit areas as was used in general. 



The only other attempt at quantitative determination of mito- 

 chondria is that by Thurlow ('17). This was done on the nuclei 

 •of the cranial nerves of the white mouse by utilizing sections 4 m 



