DISSOCIATION AND TRANSFORMATION 169 



cells exercising all their special functions, and seems to be a nor- 

 mal constituent of the cell and not a product of katabolic processes. 

 Whether such transformations ever take place in the animal 

 body, in health or in disease, and if they do what causes bring 

 them about, together with the yet broader problems of the origin 

 of various types and the influences which established their differ- 

 ent biological identities, are all questions that are attracting in- 

 vestigators in this branch of science. Whether this fundamental 

 function of Pneumococcus can be so perverted as to bring about 

 the transmutation of this organism into one of a different species 

 is a problem which has been attacked in a more general way. 



Transmutation of Species 



The mutability of members of the bacterial tribe Streptococ- 

 caceae has long been a moot question. From time to time there have 

 appeared reports of the change of a pneumococcus into a strepto- 

 coccus, and even of a swing through the whole cycle from virulent 

 Pneumococcus to Streptococcus viridans to Streptococcus hae- 

 molyticus and back to Pneumococcus. But, in these later days of 

 refined bacteriological and immunological technique one has been 

 inclined to look somewhat askance at such claims. The idea has, 

 however, persisted, and what was looked upon as a mere notion is 

 now becoming so much more than a hypothesis that there are those 

 who would accept this metamorphosis as an accomplished fact. 



There is no call to recite at any length the accounts of the early 

 experiments. Some were based on crude, faulty methods which al- 

 ways raise doubts as to the purity of the cultures the pioneers 

 studied. Disregarding claims resting solely upon morphological or 

 cultural phenomena, it is better to confine the discussion to re- 

 ports, with a few exceptions of historical interest, that have been 

 published since the development of modern bacteriological and 

 serological technique. In 1891, Kruse and Pansini, 763 by trans- 

 planting forty-six strains of pneumococci on media unfavorable to 

 growth, developed eighty-four varieties that exhibited differences 



