THE BACTERIAL NATURE OF MITOCHONDRIA 39 



The major portion of these culture experiments have been 

 made with Hver tissue of fetal and new-born rabbits. 

 Other tissues of fetal and new-born rabbits, guinea pigs, 

 dogs, and cats have also been tested. Growths similar to 

 those described have been obtained from fat, kidney and 

 suprarenal of the above named animals. There is no reason 

 to beUeve that the mitochondria of the liver are funda- 

 mentally different from the mitochondria of other cells, and 

 that they alone are bacterial in nature. 



The question has been raised, and it deserves consideration 

 here: What grounds are there for calling mitochondria 

 "bacterial in nature" or bacteria; why are they not to be 

 considered merely a part of the cytoplasm which has 

 properties of self-perpetuation and independence under 

 proper artificial conditions? This is a pertinent question, 

 and it strikes at the root of the theory that I have advanced 

 in explanation of the fundamental significance of mito- 

 chondria. The complete answer to the question can not 

 be given in a few words, for in the attempt to answer this 

 question one must deal with indefinable matter. In the 

 first place, if we seek a definition of bacteria, we are unable 

 to find an adequate one in the text-books on bacteriology. 

 Indeed, we have a mental conception of a type of organism 

 when we use the word ''bacterium." Morphologically, we 

 differentiate bacteria from unicellular plants and animals 

 by the absence of an organized nucleus. This does not 

 constitute a definition of bacteria, however, nor would a 

 catalogue of their physiological and morphological attri- 

 butes constitute such a definition. A definition would have 

 to go farther and include a statement of what they are in 

 relation to the earth and the life that it contains. There has 

 been, in recent years, a growing conception of what bacteria 

 really are. The suggestion that they are jjrimordial organ- 

 isms indicates such a trend. Again, the difficulty of dis- 

 tinguishing between some of the lowly, supposedly, pro- 



