STUDIES OF CHOLERA.' 



By Harry T. Marshall. 

 (From the Biological Laboratory, Bureau of Science, Manila, P. I.) 



I. VARIATIONS IN VIRULENCE. 



During the past year or more we have been continuing the studies of 

 cholera at this laboratory, previous reports upon this subject having been 

 published by Dr. Strong. In this paper I will review the results obtained 

 up to the present time. 



The experiments which I have conducted were undertaken with the 

 view of continuing certain investigations upon the variation of bacteria 

 with special reference to their so-called immunization. This research 

 was begun a few years ago with the dysentery bacillus. 2 At that time we 

 came to the conclusion that selection and variation are constantly mani- 

 festing their action upon bacteria, and that these processes probably play 

 an important part, not only in the rise of epidemics, but also in the 

 develorunent of each individual case of an infectious disease, in such a 

 manner that in a case of infection a large number of the bacteria are 

 killed by the host, while a relatively small number become adapted to 

 their environment, survive, multiply and produce the disease. At that 

 time, we were able by growing the dysentery bacillus upon media con- 

 taining anti-dysenteric serum, to develop a variety of bacillus which 

 not only was not agglutinated or impeded in its growth by the antiserum, 

 but which actually flourished more luxuriantly in the presence of the 

 serum than it did under other conditions and which no longer united with 

 the agglutinins in specific antidysenteric serum. A preliminary attempt 

 was made in this laboratory to repeat the same experiment with the 

 cholera vibrio. Two or three stock cultures were inoculated into bouillon 

 or peptone solutions containing small amounts of anticholera serum and 

 after intervals varying from a clay up to a week or more, transplants 

 were made into fresh flasks of bouillon containing anticholera serum. 

 As many as ten. successive transplants in one series were made after this 



1 Read at the Fifth Annual Meeting of the Philippine Islands Medical Associa- 

 tion,. February 28, 1908. 



3 Marshall and Knox: J. Med. Research (1906), N. S. 10, 325. 



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