8 



although as to the time required for this process of cleansing 

 the various observers are not agreed ; thus, while my experi- 

 ments in 1894-1895 would indicate the duration of vitality of 

 the B. typhosus in the oysters to be three weeks, Chante- 

 messe at first recommended about the same period (quelques 

 semaines), later he reduced the time to 8 days (I.e. 9 June, 

 1896). Professors Herdman and Boyce, I.e. p. 54, say: 

 " In our experiments in washing infected oysters in a stream 

 of clean sea water .... there was a great diminution or total 

 disappearance of the typhoid bacilli in from one to seven days." 



In order more accurately to determine the vitality of the 

 typhoid bacilli in oysters, and to ascertain how and in what 

 period a given number of B. typhosus introduced in or in- 

 gested by oysters, disappears from their (oysters) interior 

 under conditions resembling those obtaining in nature more 

 or less, the Worshipful Company of Fishmongers have 

 charged me with undertaking the required experiments, not 

 only with oysters, but also with mussels and cockles. Such 

 numerical determination is at present possible, and a matter 

 comparatively easy to achieve, as will presently appear when 

 describing the method used. 



It must be obvious that as regards oysters the problem 

 resolves itself into the following questions, viz. : 1. Given 

 clean oysters, i.e., oysters which are laid down in clean water, 

 what power, if any, have such oysters to destroy or eliminate 

 a definite number of B. typhosus injected into or ingested by 

 them, and further in what time can they do this, supposing 

 that they are afterwards kept under conditions best for such 

 destruction or elimination, i.e., kept in clean water daily 

 renewed ? The answer to this question would demonstrate 

 in an absolute way whether or not such power is inherent 

 in the oyster. 2. Is there any difference in these respects 

 between oysters which are derived from clean layings and 

 oysters derived from initially sewage polluted beds ? 3. Is 

 there any difference, and what, between oysters previously 

 infected with the B. typhosus, which are then kept in clean 

 sea water continually changed, and such as having been 

 infected are not placed under these favourable conditions ? 



