26 SYMBIONTICISM AND THE ORIGIN OF SPECIES 



at first directed toward testing experimentally the reactions 

 of bacteria to those agents that had been used in determining 

 the ' 'characteristics' ' of mitochondria. The complete details 

 of these and the subsequent investigations may be found 

 in the original papers, a hst of which is given in the bibli- 

 ography at the end of this book. The following resume 

 contains the chief results obtained in these researches. 



The properties that had been specifically attributed to 

 mitochondria and had been assumed to be distinct from 

 those of bacteria are in the nature of reactions which will 

 be considered under the following classifications: Staining 

 properties, reactions to various chemical and physical 

 agents, and thermal responses. The assumed chemical 

 constitution of mitochondria was largely based on the sum 

 total of these various reactions. 



Staining properties. While most of the mitochondrial 

 stains have not been considered specific for mitochondria, 

 one stain, Janus green B (vital stain) has been placed in this 

 category by Cowdry. A number of the mitochondrial 

 stains were applied to bacteria and it was found that many 

 strains of bacteria were stained like mitochondria by these 

 methods. The Janus green B vital method was also appUed 

 to various strains of bacteria. Some varieties were very 

 poorly colored by this method, but others, particularly the 

 pneumococcus and Bacterium coli were stained in a homo- 

 geneous manner like mitochondria. It is evident from the 

 results of these experiments that the staining reactions do 

 not indicate any fundamental differences between mito- 

 chondria and bacteria. 



Mitochondria were also subjected to bacteriological stain- 

 ing methods. This was done on smear preparations of tis- 

 sues from fetal and young animals. They were treated like 

 ordinary bacterial smears. The following bacteriological 

 stains were used: Loeffler's methylene blue, pyronin-methyl 

 green, the Giemsa stain and Gram's method. The mito- 



