VARIATIONS IN TYPHOID BACILLI^ 



KAN-ICHIRO MORISHIMA 



Department of Bacteriology, College of Physicians and Surgeons, Columbia 

 University, New York City 



Received for publication September 10, 1920 

 INTRODUCTION 



Just as there is often great difficulty in diagnosing atypical 

 clinical conditions, so great difficulty may be experienced in 

 identifying bacteria which develop abnormal characteristics. 

 The acquisition, by individual strains of many species of bacteria, 

 of morphological and cultural characteristics which differ from 

 the usual type has been noted by many observers and has been 

 referred to more or less loosely by several different terms. Thus, 

 Neisser (1906) and Massini (1907) used the word "mutation" 

 to designate atypical forms of Bad. coli, Pringsheim (1911) 

 speaks of an "adaptation" of bacteria, and Gurney-Dixon (1919) 

 uses the term "transmutation." 



We can sometimes follow such variations by gradual changes, 

 from one stage to another, during which the bacteria pass through 

 a process of evolution, adapting themselves to their surroundings. 



Such variations may consist in the acquisition of new morpho- 

 logical, biochemical, or serological characters, in the loss of 

 similar properties, or the two processes may occur at one and 

 the same time. The change may be sudden or gradual, and is 

 generally retained by the offspring. 



The study of such variations is of fundamental importance to 

 an understanding of the bacteria and may have considerable 

 botanical importance since it would seem that processes of 

 evolution or adaptation could be most easily investigated with 



1 Submitted in partial fulfillment of the requirements for the degree of Doctor 

 of Philosophy, in the Faculty of Pure Science, Columbia University, May, 1920. 



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