EDITORIAL,. 187 



food might easily become infected and become a means of propagating 

 the disease. 



Dr. Marshall, Biological Laboratory, Bureau of Science: In concluding 

 I wish to call attention to one statement made by Dr. Heiser to the 

 effect that the cholera vibrio does not seem to abate in virulence while 

 passing through animals and he concluded that some external cause 

 produced the fall of epidemics. My experiments prove that the viru- 

 lence may diminish most markedly even under favorable conditions of 

 passage through animals. 



Buffer has also shown that the virulence of bacteria, identical with 

 cholera culturally and in other ways, is subject to great variation. In 

 this connection I also wish to call attention to Dr. Clements's statement 

 and emphasize the extreme rapidity with which variation from nonviru- 

 lent to virulent bacteria may take place. In experiments with organisms 

 of dysentery a nonagglutinating variant can be produced within the space 

 of a few hours. 



Dr. Heiser's hypothesis of gradual immunization through repeated in- 

 fections with mild or nonvirulent strains of cholera is interesting, but it 

 can not be said at present whether this is a feasible means of immuni- 

 zation or not, "possibly, a local immunity of the intestine may result, but 

 the observations do not show that a general immunity may follow. The 

 results of the ingestion of bacteria or of toxins are not conclusive. 



In referring to some remarks made by Dr. Musgrave I wish to state 

 that it is usual for the cholera vibrio to be killed in the presence of 

 ordinary saprophytic bacteria, and it is usually stated that it dies rapidly 

 in sewers. I have not encountered in the literature accounts of any 

 experiments in which a symbiotic condition favorable for cholera has 

 been developed. 



DISCUSSION OF THE PAPER BY DR. EDWARDS. 



Captain Ryley, B. A. M. C, Hongkong: When an epidemic occurs 

 in tropical countries it is usual for the people to drink distilled water 

 or soda water. I inocidated soda water artificially with cholera organisms, 

 and I found that the usual pressure of about 150 pounds to the square 

 inch, which it is believed should destroy pathogenic bacteria, had no 

 effect on the cholera vibrio. The soda water was of the variety which 

 is made by impregnating the water with carbonic-acid gas. I was able 

 to recover the cholera organism from the water which I worked with. 



Dr. Carpenter, United States Navy: At the Cavite Naval Station for 

 the past year we have had experience with artesian well water. We 

 found that the water which came from a depth of 508 feet was infected 

 when it first came through the pump and we began to employ boiled 

 water. This was not sufficient to supply several thousand people and we 



