THE MITOCHONDRIAL CONSTITUENTS OF PROTOPLASM. 83 



VIII. CHEMISTRY. 



THE CONSTITUTION OF MITOCHONDRIA. 



It is an interesting and rather unusual occurrence, in the study of mitochondria, 

 for three independent Unes of investigation to yield similar results, yet Regaud 

 (1908d, p. 720), in the first place in the study of mammalian tissues, Faure-Fremiet 

 (1910a, p. 622), who worked on protozoa, and the botanist Lowschin (1913, p. 203; 

 1914, p. 269) have all arrived at the conclusion that mitochondria are, chemically, 

 a combination of phosphoUpin and albumin, which, in itself, speaks very strongly 

 in favor of the unity of the class of granules under consideration. The evidence is 



briefly this : 



(1) Mitochondria are almost completely soluble in alcohol, chloroform, ether, 

 and dilute acetic acid. They are rendered insoluble by chromization. They are 

 not doubly refractile and they do not stain with either Sudan III or Scharlach R. 

 They are only sometimes blackened with osmic acid. 



(2) It is" said that part of the mitochondrial substance is not soluble in these 

 fat solvents and it is supposed that this portion is albumin (see also Bullard, 1916, 

 p. 26), for formahn and bichromate, which are used as fixatives for mitochondria, 

 are energetic coagulants of albumin. IVIillon's reagent is the only color-test for 

 protein which can be satisfactorily apphed to material in section (the xanthoproteic 

 reaction may also be used, but it is less satisfactory because it is more destructive). 

 I learn from Dr. R. R. Bensley that the mitochondria do not give a definitely posi- 

 tive Millon reaction in comparison with the strong Millon reaction which is given 

 by such cytoplasmic structures as the zymogen granules. Even if there were a 

 change in color in the mitochondria it might not be of sufficient intensity to be 

 appreciated in filaments of such extreme fineness as mitochondria (0.2 micron in 

 diameter) embedded in a colored cytoplasm. I have obtained no success with the 

 xanthoproteic reaction. Mitochondria do not give any of the color reactions of 

 polysaccharides. 



(3) Artificial mitochondria have been made by Lowschin of lecithin in differ- 

 ent salt and albumin solutions (resulting in the formation of lecithalbumin), which 

 apparently present the same form and solubilities as true mitochondria. They 

 form granules, rods, and filaments which, he claims, multiply by division. He 

 embedded them in glycerin-gelatin, fixed them, and found that they stained in 

 the usual way by the various mitochondrial methods. 



(4) The temperature solubiUty of mitochondria may also be significant. It 

 has been discovered by Policard (1912rf, p. 229) in the case of animal tissues and by 

 N. H. Cowdry (1917, p. 220) in plants that the mitochondria are soluble at a tem- 

 perature from 48° C. to 50° C, while the other parts of the cells remain practically 

 unaffected. Phosphatids have a low melting-point also. 



(5) Apparently the specific gravity of mitochondria is somewhat greater than 

 protoplasm (Faure-Fremiet, 1913, p. 602). This is determined by the centrifuge 

 method. If they are thrown down they are said to be of high specific gravity. 

 If the protoplasm is in the physical condition of a "gel" rather than a "sol," as in 



