PREFACE 



The study of mitochondria in recent years has come to 

 occupy an important position in biology. Two points of 

 view are held in regard to the nature of these microscopic 

 structures, and this circumstance appears to be responsible 

 for the diversity of opinion as to the activities of these bodies. 

 The most commonly accepted view holds that mitochondria 

 are cell-organs derived from the cytoplasm. The other 

 view, that they are microorganisms "symbiotically" united 

 to the cell, has attracted only a few adherents, and ap- 

 parently has been looked upon as a fantastic and improbable 

 theory. 



The bare statement that all living cells of plants and 

 animals contain small bodies that are independent entities 

 capable of a free existence, or in other words, that all cells 

 contain bacteria or microorganisms, is, perhaps, a little 

 shocking to those who hold dogmatic ideas on cell physi- 

 ology. The recent advances in physical chemistry also 

 have served to direct our thoughts and notions on "life- 

 organization" into channels which would belittle the 

 importance of "life" in the organization of protoplasm. 

 Obviously, physical and chemical forces play a role of fun- 

 damental importance in the morphology and physiology of 

 living organisms, but we are still groping in ignorance as to 

 the real nature of living matter, and we are not at liberty 

 to forget or belittle the significance of "life" in the analyses 

 of living bodies. 



During the past seven years the author has investigated 

 the nature of mitochondria, and has arrived at the unquali- 

 fied conviction that these bodies in the cell are bacterial in 

 nature. The evidence for this conclusion has been published 

 in a series of papers. It has been evident that a large 



