THE MITOCHONDRIAL CONSTITUENTS OF PROTOPLASM/ 



By E. V. CowDRY. 



INTRODUCTION. 



Schultze defined the living substance, protoplasm, as being a glass-like, semi- 

 viscid material in which granules are embedded. We have been permitted to go a 

 step further, because we can now recognize among these granules a definite class, 

 which we call mitochondria and which, within a surprisingly short space of time, 

 have been described in the cells of all tissues, in the adult condition and in all stages 

 of development. They have been found in rapid succession in all organisms which 

 have been studied, from the protozoa to man, and from certain of the algse to the 

 highest of plants. It has become apparent that they are inseparable from living 

 protoplasm and that they yield place to no other visible constituent of living 

 matter in breadth of distribution. Their characteristic form (strongly suggestive 

 of bacteria), their lipoid properties, and their extraordinary sensitivity to certain 

 types of pathological change have become familiar. These and other discoveries 

 have stimulated interest in many quarters and have given rise to hastily conceived 

 and poorly supported theories and to much discussion, with the result that ideas 

 of cell structure have been, in large measure, recast. 



Recognizing the importance of this new line of work, I have attempted to set 

 forth our present knowledge of mitochondra and their significance from the 

 standpoint of cell development and cell function, making use of unpublished 

 observations of my own and of the literature on the .subject. In a field so large it 

 has been necessary to choose and select, to elaborate some points and to leave 

 others almost untouched, so that many important contributions have been passed 

 without mention. At first the researches on mitochondria were purely descriptive, 

 but now they have taken an experimental turn, and it is this aspect of the subject 

 which I venture to emphasize. 



From the beginning, the Department of Embryology of the Carnegie Insti- 

 tution of Washington has placed valuable apparatus at my disposal. The work 

 was carried on in the Anatomical Laboratory of the Johns Hopkins University, and, 

 during the summer of 1916, at the Marine Biological Laboratory, Woods Hole. 

 It has been completed through the action of the Peking Union Medical College in 

 giving me the freedom and the time necessary during the past year. 



I. HISTORICAL REVIEW. 



It is impossible to say who first discovered mitochondria, for, with the out- 

 burst of interest in cell granulations between 1870 and 1890, coincident with the 

 introduction of ajjochromatic lenses, mitochondria were observed and described 

 by many authors under very diverse names. Unhappily, however, this group of 



'Contributions from the .\natoniical Laboratory, Peking Union Medical College No. 1. 



41 



