MITOCHONDRIA IN PLANT AND ANIMAL CELLS. 2 19 



Composition. 



We must bear in mind the unsatisfactory nature of the evidence 

 upon which our views of the chemical constitution of mitochon- 

 dria are based. It is impossible to make a direct chemical 

 analysis of them. We are forced to use solvents, special stains 

 and so forth. We know astonishingly little positively, but we 

 infer a great deal, often on very insufficient grounds. Most of 

 the work has been done with animal cells, and investigators 

 have arrived at the general conclusion that here mitochondria 

 are of the nature of phosphatids, in other words, that they contain 

 fatty acid, phosphoric acid, glycerol and some nitrogen base. 

 Lecithin is an example of a typical phosphatid and has been 

 used to manufacture artificial mitochondria. Briefly the evi- 

 dence is as follows : 



1. In animal cells it has been found that mitochondria are 

 almost completely soluble in alcohol, ether, chloroform and 

 dilute acetic acid. They are rendered insoluble by chromiza- 

 tion, and also, in my experience, by treatment with formalin, 

 at least in some cases. They do not stain with Sudan III. or 

 Scharlach R. They are only sometimes blackened with osmic 

 acid. 



In plant cells they are also soluble in alcohol, ether, chloroform 

 and dilute acetic acid and they are here rendered insoluble by 

 chromization in exactly the same way. Treatment with formalin 

 also makes the mitochondria insoluble. The whole cell blackens 

 with osmic acid so readily that it is impossible to ascertain just 

 how strongly the mitochondria themselves react to it. 



2. It is said, in the literature, that part of the mitochondrial 

 substance, in animal cells, is not soluble in these fat solvents and 

 it has been assumed that this portion is albumin. The results of 

 applying Millon's reagent are uncertain and difficult to interpret. 



In view of the statement of Forbes and Keith ('14, p. 73) 

 that vegetable phosphatids differ from those in animal cells 

 in that they nearly always contain sugar firmly bound to the 

 rest of the molecule, we should bear in mind the possibility of 

 sugar being a likely constituent of mitochondria in plants. 



3. Artificial mitochondria have been made by Lowschin ('13, 

 p. 203) of lecithin and albumin solutions which apparently 



