THE BACTERIOLOGY OF THE OYSTER AND OTHER SHELLFISH. 
43 
B. colt. — (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 Gronvth 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 arc added to the water, their presence may be 
demonstrated longer than in cases where smaller quantities arc 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 does in sea-water in the laboratory, but 
*Proc. Roy. Soc, vol. LVI., p. 440. 
