FUNCTIONAL SIGNIFICANCE — MITOCHONDRIA 433 



fluctiiations in the mitochondrial content. The observations 

 ^la^-e not been controlled by a careful estimation of cell volumes. 

 Thurlow ('!(), p. 253) has been the first to realize these discrep- 

 ancies. She has established a definite mitochondria cytoplasmic 

 ratio in the nerve cell just as Hertwig years ago measured the 

 nucleus cytoplasmic ratio. 



There have been no carefully checked observations on quali- 

 tative changes in mitochondria with cell activity notwithstand- 

 ing the fact that we have abundant evidence to show that the 

 solubilities of mitochondria do vary. Of course the changes 

 in form of mitochondria have been subjected to careful scrutiny, 

 but so far they have yielded us little of value. The observa- 

 tions of Holmgren ('08, p. 308) on the changes in mitochondria 

 in muscular fatigue are qualitative in a sense, and very interest- 

 ing, but they have never been confirmed. 



Relying on this rather meagre information investigators are 

 generally inclined to believe that mitochondria participate 

 in some of the processes involved in cell metabolism. Coghill 

 ('15, p. 350) is rather more- specific for he relates mitochondria 

 to the constructive side of metabolism. Mayer Rathery and 

 'Schaeffer ('14, p. 619) attempt to narrow down the function of 

 mitochondria still further. They claim that they take part 

 in the processes of oxidation and reduction. This suggestion 

 has also been tentatively advanced by the Lewises ('15, p. 393). 

 It is in accord with the fact that mitochondria occur in all plants 

 which have been examined, with the possible exception of some 

 of the lower algae and bacteria, though I have even found gran- 

 ules staining specifically with janus green in some of the latter. 

 It also falls in line with what we know of the janus green reaction. 



RELATION TO HISTOGENESIS 



The origin of the idea that mitochondria are concerned with 

 histogenesis is not difficult to trace. They occur in all embryonic 

 cells. In early stages of development they are the only formed 

 elements in the cytoplasm. They are filamentous in the mjo- 

 blasts and neuroblasts and it is perfectly natural to think that 



