338 NORMAN CLIVE NICHOLSON 



tion is, however, ruled out, by the fact that in other tissues the 

 mitochondria may still be filamentous even though they be in- 

 creased greatly in amount (Policard, '10, p. 284). 



The variations in the form of mitochondria must be due to dif- 

 ferences in themselves or in their environment or in both. 



There is evidence that the chemical constitution of mitochon- 

 dria is different in different cells. Regaud ('10, p. 301) has 

 shown that there is a progressive increase in the resistance of 

 mitochondria to acetic acid in the course of spermatogenesis. 

 My experiments have shown that the mitochondria in the nerv- 

 ous system also differ in their susceptibility to acetic acid. In 

 the nervous system this difference in chemical behavior does 

 not seem to be related to a difference in morphology, as mito- 

 chondria of quite different form exhibit similar solubilities. So 

 much for chemical composition. Now with regard to density, 

 the only indicator which I have is the difference of intensity in 

 staining with fuchsin and as I have said this is not uniform and 

 is of uncertain meaning. That the form of mitochondria is, in 

 a measure dependent upon their own organization is evident 

 when we remember that if the long filamentous mitochondria in 

 the acinus cells of the pancreas are squeezed out of the cell 

 into the surrounding fluid they maintain their original form, 

 unaltered, for a surprisingly long time. 



As to the differences in the cytoplasm in which the mito- 

 chondria are embedded I have observed that the cells of the 

 mesencephalic nucleus of the trigeminal nerve are more notice- 

 ably shrunken in some preparations than the other cells in the 

 vicinity, which may be accounted for on the assumption of a 

 higher water content. The difference in form of mitochondria 

 and of water content of their surroundings may not be unrelated. 

 As has been noted the mitochondria are invariably filamentous 

 in the processes, though they may sometimes be granular in 

 the cell bodies. This led to the belief, that there might be 

 a difference in water content in gray and white substance of the 

 brain, which curiously enough, was found, on looking up the 

 literature, to be actually the case. The possible influence of the 

 water content seems the more hkely since Lowschin ('13, p. 203) 



