THE MITOCHONDRIAL CONSTITUENTS OF PROTOPLASM. 133 



way to dififerent varieties of injurious influences — in other words, that there is 

 nothing specific in the reactions of mitochondria to pathological change — is also 

 in accord with the prevalent conception that they take part in a type of activity 

 common to many cells, at which the noxious influences strike. 



Relying on this confessedly inadequate information, investigators generally 

 are inclined to believe that mitochondria participate in some of the processes 

 involved in cell metabolism. Coghill (1915, p. 350) is rather more specific, for he 

 relates mitochondria to the constructive side of metabolism. But the term "metab- 

 olism" is very vague. Its meaning has changed from Michael Foster's original 

 definition. It is now used to designate a multitude of chemical reactions from the 

 taking in of foodstuffs to the elimination of waste products, including even cellular 

 oxidations and reductions. We have metabolism of carbohydrates, fats, and 

 proteins to deal with. Mitochondria occur in organisms entirely independently 

 of their diet. They are just as abundant in herbivors as in carnivors; and many 

 of them are contained in green plants, which obtain their nitrogen from nitrates, 

 their hydrogen from water, and their carbon from the air. Where metabolism 

 varies in kind, they apparently do not vary. They can hardly be a stage in the 

 utihzation of a specific substance taken in in the food, much less a waste product. 

 They must be built up in the jihylogenetic scale in a variety of different ways to 

 serve a common function. We naturally inquire whether they are reserve products 

 or whether they play an active part in cell metabolism. 



The experiments of Russo (1912, p. 203) would seem to indicate that mito- 

 chondria are reserve food products. He claims that their number may be increased 

 in the ovarian eggs of chickens fed with lecithin. His conclusions receive some 

 indirect support from the work of R. Van der Stricht (see p. 84), but his experi- 

 ments have never been repeated, in spite of the great interest which attaches to 

 them. We are very much in need of information along these lines and it seems 

 that experiments on the effect of inanition and of different diets on the mitochon- 

 dria in mice might yield valuable results. The monograph by Champy (1911, 

 p. 146) on the behavior of mitochondria in intestinal epithehal cells would serve as 

 a good point of departure. 



Regaud (1911, p. 685) thinks that mitochondria play actively the part of 

 plasts, choosing and selecting material from the surrounding protoplasm and from 

 the blood-stream, condensing them and converting them, in their substance, into 

 diverse products. He likens them to the hypothetical side-chains of Ehrlich, and 

 his idea is an extension of the famous lipoid membrane theory of Overton ; in other 

 words, he believes that they function in constructive metabolism. They may 

 act as a sort of vehicle or medium in which chemical reactions take place. 



RESPIRATION. 



Kingsbury (1912, p. 46) was the first to suggest that mitochondria play an 

 important part in iirotf)plasmic respiration. He says that osmic acid, potassium 

 bichromate, and formalin, which are the chief ingredients of mitochondrial fixa- 

 tives, are preeminently oxidizers and that their efficiency depends on the presence 



