THE BACTERIOLOGY OF THE OYSTER AND OTHER SHELLFISH. 43 



B. coli. — (i) Fermentation; rate of gas formation variable. (2) Indol reaction; not 

 constant. (3) Milk coagulation ; constant. (4) Potassic iodide potato gelatine ; abundant 

 growth. (5) Behaviour in gelatine ; diffusion very variable, in many cases less rapid 

 than with B. typhosus. (6) Motility ; very variable. 



This preliminary investigation proved of great service in familiarizing ourselves 

 with the appearances of typhoid and colon bacilli, and prepared the way for the subsequent 

 investigations. 



II. — The Action of Sea-Water upon the Growth of the B. typhosus. 



Eight experiments were made to ascertain whether the B. typhosus was capable 

 of multiplying in sea-water. The subject was naturally one of very considerable import- 

 ance in connection with the liability of oysters to infection when grown in sewage- 

 contaminated water. Our experiments showed that sea-water was inimical to the growth 

 of the B. typhosus. 



When a large number of bacilli are added to the water, their presence may be 

 demonstrated longer than in cases where smaller quantities are used. Fourteen days 

 would appear to be the average duration in sea-water incubated at 35° C. ; whilst, kept 

 in the cold, their presence was demonstrated, as will be seen by experiment VII., on 

 the twenty-first day. There appears to be no initial or subsequent multiplication of the 

 bacilli. Between forty and seventy hours after infection there is less decrease than at 

 other periods ; but there is no evidence of increase in numbers of the bacilli, when 

 grown in sea-water, either when incubated or at ordinary temperatures. Dr. Klein, in 

 his Report, states that in no instance did he find evidence of multiplication of the 

 bacilli in the sea-water. He was able to recover the bacillus up to the fourth week. 

 In 1889, Giaxa made a series of observations upon the vitality of the B. typhosus in 

 sterilized and non-sterilized sea-water, and showed that it was present in the latter up 

 to the ninth day, and in the former to the twenty-fifth. In this connection may be 

 taken the observation of Frankland and Ward,* that a 3 per cent, salt solution most 

 prejudicially influences the growth of the B. typhosus, the latter disappearing by the 

 eighteenth day. Experiments similarly conducted upon the propagation of the B. typhosus 

 in fresh water have yielded similar results. Thus Kraus showed that a very rapid 

 decline of the bacillus, and a very rapid increase of the ordinary sea-water bacteria, 

 took place when the water was incubated. Frankland and Ward showed that the 

 bacillus disappeared at the end of thirty-four days in unsterilized Thames water, and 

 that there was no multiplication in potable water. 



How far all these laboratory experiments may be taken as indicating what 

 actually takes place in nature, it would be difficult to say. The bacillus probably does 

 perish in a short time in the sea, just as it docs in sea-water in the laboratory, but 



* Proc. Roy. Soc, vol. LVI., p. 440. 



