MITOCHONDRIA IN TISSUE ' CULTURES 393 



Numerous observers have claimed that they form the fat directly 

 (Altmann '89-'95, Metzner '90, Zoja '91, Arnold '07, Russo 

 '07, Loyez '09, Van der Stricht '05, PoHcard '09, Frissinger 

 '09, Regaud '10, Faure-Fremiet '10, Dubreuil '13); indirectly 

 (Bluntschli '04, Van der Stricht '05, Van Durme '07, Lams and 

 Doorme '08, Schoonjans '08). It is claimed that they form the 

 leucoplastids, chloroplastids and chromoplastids and possibly the 

 glycogen (Guilliermond '12-' 13). 



The above theories seem impossible to correlate. It seems 

 evident that the mitochondria are too universal in all kinds of 

 cells to have the function of forming any one of the above struc- 

 tures of differentiated tissue, and in the light of what cytological 

 chemistry is known, it appears practically impossible for the 

 mitochondria to form all the cell structures mentioned above. 

 In view of the fact that the mitochondria are found not only 

 in almost all animal cells but in plant cells as well it seems 

 more probable that they play a role in the more general physi- 

 ology of the cell. It may be possible that they are concerned 

 with respiration. As suggested by Kingsbury ('12), they may 

 represent the structural expression of the reducing substances 

 concerned in cellular respiration, which process Matthews ('05) 

 has described in his theory of protoplasmic respiration. Accord- 

 ing to Matthews, the activity of the cell causes reducing bodies 

 to be formed in the cytoplasm for whose neutralization oxygen 

 is necessary. The lipoid nature of the mitochondria makes it 

 possible to consider them as reducing bodies and certainly the 

 mitochondria exhibit activities which may be due to the fact 

 that they are continually formed in the cytoplasm and con- 

 tinually oxidized. On the other hand, the mitochondria may 

 have to do with assimilation or they may even be stored-up 

 food-stuff themselves, which are continually used up and restored 

 again. Beckwith ('14) holds that the mitochondria are unneces- 

 sary for the life of the cell or for the development of such a 

 complicated structure as a Hydractinia ciliated planula. The 

 fact that such a large group of observers should each have evi- 

 dence to show that the mitochondria form some one structure 

 of the differentiated cell shows that the mitochondria must be 



