FOOD-POISONING BACILLI 379 



twelve hours, and then plates of Conradi-Drigalski medium are inoculated 

 from it. For investigation of faeces, a medium made up as above but with 

 ordinary st<-rilr water may be inoculated and a similar procedure followed. 

 On the whole there is little to be gained from this attempt to isolate the 

 typhoid bacillus from water in any particular case, and it is much more 

 useful for the bacteriologist to bend his energies towards the obtaining 

 of the indirect evidence of contamination of water by sewage, to the 

 nature of which attention has been called in Chapter V. 



THE PARATYPHOID AND FOOD-POISONING BACILLI. 



In the b. coli we have an organism having a definite habitat 

 in the animal intestine, and presenting certain cultural characters 

 by which it may be recognised. We may look on the bacillus 

 typhosus as an organism of the same class whose cultural 

 reactions as compared with b. coli present somewhat negative 

 characters, but which acquires definiteness from its association 

 with a well-known clinical condition. We have now to deal 

 with a group of organisms which occupy rather an intermediate 

 position between the two organisms referred to, and whose 

 cultural characters are such as to make their differentiation from 

 either fairly practicable. The members of this group have been 

 originally described in association with a variety of clinical 

 conditions, but, notwithstanding, they resemble each other so 

 closely that great difficulty arises, and the recognition of different 

 types which in literature receive different names can only be 

 effected by the application of the finest bacteriological tests. 

 Although in cultures the different types present slight differences, 

 these are not sufficient for the assignment of a name to an 

 organism of the class isolated from some fresh source, and, as a 

 matter of fact, in modern work relating to them, it is generally 

 impossible in identifying an organism to rely on merely noting 

 a correspondence with a described type. The method usually 

 adopted is to obtain from other workers cultures of what may 

 be called the historic strains isolated, and by comparing the 

 organism under investigation with these, to attempt to place it 

 in its proper position. 



Organisms of the group are of great importance, not only 

 from their producing ordinary infective disease in man, but 

 because they are the agents at work in the great majority of 

 the not infrequently occurring cases of illness usually described 

 as " food poisoning." l Such poisoning is often referred to as 

 " ptomaine poisoning," from the idea originally prevailing that 



1 A special type of food poisoning is associated with the Bfn-illi's l>tulinm, 

 fj.v. 



