THE MITOCHONDRIAL CONSTITUENTS OF PROTOPLASM. 43 



In a review of this sort, one can not help being impressed with the existence of 

 certain definite landmarks which have determined the whole trend of subsequent 

 investigation and about which our ideas revolve. It can not be denied, for 

 instance, that Meves's generalizations and theories, unjustified though they may 

 be, have exercised a most stimulating effect upon the study of mitochondria. His 

 statement (1908, p. 845), prompted by the discovery of mitochondria in all 

 embryonic tissues, that all cellular differentiations are formed from mitochondrial 

 coming at a time when the origin of these differentiations had been more or less 

 explained to the satisfaction of cytologists without reference to mitochondria, 

 attracted world-wide attention. Much work was hastily done anew with the 

 most conflicting results, and even now uncertainty prevails in all branches of histo- 

 genesis. Similarh', his doctrine that mitochondria constitute in part the material 

 basis of heredity, supported by the discovery that they enter the egg on fertili- 

 zation, coming just when the chromatin hypothesis was receiving its strongest 

 support at the hands of Morgan and others, could not fail to attract attention. 



We owe much to Regaud (1908rf, p. 720) and his school for supplying, through 

 skillful indirect methods, the first accurate information regarding the chemical 

 constitution of mitochondria, according to which they are made up of a com- 

 bination of phospholipin and albumin. This immediately clarified our ideas, 

 enabled us for the first time to form some estimate of their potentialities, and 

 served as a point of departure for many investigations of value. It is important 

 also to note that Regaud has thus brought the whole work on mitochondria into 

 line with the recent tendency among physiological chemists and pathologists to 

 become interested in the phospholij^ins, whereas formerly their whole attention was 

 devoted to the stud>' of proteins, being dominated by the tremendous impetus of 

 Eniil Fischer's work on protein synthesis, which attracted world-wide notice because 

 of the psychological factor involved in the supposed manufacture of living substance. 



The introduction of the dye janus green opened up a new and most valuable 

 method of approach by making the study of mitochondria, specifically stained in 

 living cells, so simjjle and satisfactory. It afforded an excellent basis for expe- 

 rimentation, dispelled any lurking doubt of the existence of mitochondria in the 

 living condition, and sujiplied a means of detecting the artifacts produced bj- the 

 older methods of fixation and staining. 



The adaptation of methods of tissue culture by Champy (1912, p. 987; 19136, 

 p. 188) and the Lewises (1914, p. 330) to the study of mitochondria bids fair, if 

 properly controlled, to give information of a type which can be obtained in no 

 other way. It makes possible the continuous study with the microscope of vital 

 processes going on in the cell. The Lewises in particular have devised methods 

 by which they are able to keep selected mitochondria under observation for com- 

 paratively long periods of time and to see just what they do. Yet the method has 

 its obvious limitations. In order to be most effective it should be used in con- 

 junction with the methods of cell dissection recommended by Kite and Chambers. 



And finally, the imjwrtance of the recognition of the sensitivity of mitochondria 

 to pathological change becomes quite apparent when we remember that hereto- 



