BACTERIOLOGICAL ANALYSIS. 655 



The key to the separation of Bacillus typhosus and Bacillus 

 dysenteriae Flexner, are the sugars raffinose and sorbit, and the 

 observation of the effect on litmus milk — the production or not 

 of the indol reaction, and whether motile or not. 



It will be advantageous here to briefly refer to a few practical 

 applications of the biochemical method. 



The Isolation of the Colon-like Organisms of Food Poisoning. — 

 A large number of the cases of food poisoning are associated with 

 the presence of colon organisms of the Gaertner type. This is a 

 general name including a number of closely allied organisms be- 

 lieved to be responsible for certain acute " ptomaine " poisonings, 

 with diarrhoea or pseudo-typhoid symptoms, which cases are 

 sharply marked off from botulism cases, where the symptoms are 

 mainly referable to the higher nerve centres. The first isolated 

 of these organisms was the Bacillus enteritidis of Gaertner, but 

 now the cases are known to be caused by several members of a 

 group of organisms with very similar attributes, mostly differing 

 only in their agglutination and immunity reactions. Such organ- 

 isms as B. enteritidis Gaertner, B. paratyphosus A (Schottmuller). 

 B. paratyphosus B (Schottmuller), B. certrych, B. hreslaviensis, B. 

 suipestifer, are included in this group. As shown by the inclusion 

 of B. paratyphosus A and B, which organisms, besides being the 

 apparent causes of cases of food-poisoning, are also associated with 

 tnat elusive entity paratyphoid fever, and B. suipestifer, the 

 second factor in the causation of the filter-passer-cum-bacillus dis- 

 ease, swine fever, which organism on the score of probability is 

 almost certainly the type found in some food-poisoning cases, 

 the group is one of wide interest, and the means of distinguishing 

 its members from other colon bacilli becomes vitally important. 



Faced with the problem of telling \vhether certain organisms, 

 say isolated from a brawn, the supposed cause of some food- 

 poisoning epidemic, are of this group, how do we proceed ? First, 

 referring to the table, we find they are serogenes, and then rapidly 

 we can see they are non-lactosemannit-non-saccharose arogenes, 

 and as far as definitely known dulcit is fermented. However, some 

 (suipestifer) members of this group which I possess, ferment dulcit 

 very erratically, sometimes doing so, sometimes not. Here also 

 the litmus milk observation is very useful, probably the most 

 useful single test of all. All the Gaertner group produce a very 

 slight acidity on milk, and generally, usually after the third day, 

 become progressively more and more alkaline, B. paratyphosus 

 A is said to give permanent acidity on milk, but it is questionable 

 whether it does not after some weeks gradually give rise to an 

 alkaline reaction. 



With these data it is easy enough to settle the question as to 

 whether our suspected organism is or is not of the Gaertner group. 

 If we wish further details we may employ the agglutination and 

 absorption methods, and determine its immunity reactions. 



