258 BACTERIA IN OTHER FOODS 



water, and could live for a prolonged period in water rendered opaque 

 by the addition of faecal matter. They also proved that the number 

 of organisms in the pallial cavity and rectum of oysters which had 

 been in clear water was much less than occurred in oysters laid 

 down in proximity to a sewer outfall (10 bacteria in the former case 

 as against 17,000 in the latter). It was found that more organisms 

 were present in the pallial cavity than in the rectum. B. typhosus 

 could be identified in cultures taken from the water of the pallial 

 cavity and rectum fourteen days after inspection, but in diminishing 

 numbers.* Several important links in the chain of evidence 

 remained in obscurity. It was at this time, when the matter was 

 admittedly in an unsatisfactory stage, that Dr Cartwright Wood 

 made his experiments.-]- "We have not space here to enter into this 

 work. But his conclusions seem to have been amply established, 

 and were to the effect that typhoid and cholera bacilli could, as a 

 matter of fact, exist over very lengthened periods in ordinary sea- 

 water. The next step was to demonstrate the length of time the 

 bacilli of cholera remained alive in the pallial cavity and body of 

 the oyster. Dr Wood found they did so for eighteen days after 

 infection, though in greatly diminished numbers. This diminution 

 was due to one or all of three reasons : (a) the effect of the sea- 

 water already referred to as finally prejudicial to bacilli of typhoid ; 

 (b) the vital action of the body-cells of the oyster; (c) the wash- 

 ing away of bacilli by the water circulating through the pallial 

 cavity. 



Broadly it may be said that the same principles apply to the 

 typhoid bacillus. It can live in sea- water, probably, for three to 

 five weeks (Klein, Boyce) although it does not appear to multiply 

 in this medium. Oysters infected with the typhoid bacillus can 

 retain their infective properties for two to three weeks, and even 

 if placed in running sea-water, may not lose their infective properties 

 for some days. Mosny suggested any period from one to eight 

 days. In cockles there is evidence to show that the typhoid bacillus 

 thrives and even multiplies, and these shell-fish are not rendered 

 free from infection by being laid in pure water. 



It will have been noticed that up to the present we have learned 

 that typhoid bacilli can and do live in sea-water, and also inside 

 oysters up to eighteen days, but in ever-diminishing quantities. 

 The question now arises : What is the influence of the oyster upon 

 the contained bacilli? Under certain conditions of temperature 

 organisms may multiply with great rapidity inside the shell of the 

 oyster. Yet, on the other hand, the amoeboid cells of the oyster, 



* Report of British Association for Advancement of Science, 1895 ; and Thompson^ 

 Yates Laboratory Report, vol. ii. 



t Brit. Med. Jour., 1896, ii., p. 760 et seq. 



