248 BACTERIA PATHOGENIC TO MAN 



reactions, and the group must, therefore, be composed of a number of 

 distinct races, as is the case with bacillus coli communis. The para- 

 typhoids, on the other hand, none of which has so far been isolated from 

 cases other than typhoidal, interact without exception; that is to say, an 

 active serum prepared from any one of the bacilli will agglutinate all the 

 members of the group. The paratyphoids, then, appear to be a distinct 

 species in the same sense that the typhoid bacilli are a distinct species. 

 It may be found possible to distinguish various species within the 

 paracolon group. There are certainly three members which afford 

 mutual reactions one of those isolated by Schottmiiller, one by 

 Kurth, and one by Libman and these might provisionally be called 

 ^-paratyphoids. Since, however, there are others of the paracolon 

 group which have caused typhoidal symptoms, yet do not appear to 

 belong to this particular species, it seems a little premature to attempt 

 these fine distinctions, and for the present it will be sufficient to confine 

 ourselves to the idea of the two main groups : 



I. The Paracolons. A group of bacilli, the members of which are 

 culturally alike, but constitute several distinct species, some of which 

 may give rise to typhoidal symptoms in man. 



II. The Paratyphoids. A distinct species, culturally unlike the para- 

 colon bacilli, and causes typhoidal symptoms in man. 



Pathogenicity in man has been established for other of the inter- 

 mediates. Broadly speaking there are three types of infection: 



1. TYPHOID TYPE, caused by the paratyphoid bacilli and certain of 

 the paracolons. 1 



2. EPIDEMIC MEAT-POISONING TYPE, caused by bacillus enteritidis 

 and its allies. 



3. PSITTACOSIS TYPE,, caused by bacillus psittacosis. 



In addition to these three types Griinbaum has suggested that febrile 

 jaundice may be caused by one of the intermediates. 



Bacillus icteroides (Sanarelli), which is probably an intermediate, is 

 no longer the accredited cause of yellow fever, but is considered simply 

 as a secondary invader. It is stated that it ferments dextrose and 

 saccharose. 



THE TYPHOID TYPE. The Term Paratyphoid Fever. Though 

 Gilbert introduced the terms "paracolon" and "paratyphoid" in 

 1893 to designate groups of bacilli, Achard and Bensaude (1896) were 

 the first to employ the term paratyphoid in a clinical sense. This use 

 of the term was sanctioned by Schottmiiller in 1901, and has been 

 adopted by several recent writers. On the other hand, Coleman seriously 

 questions whether the term should be recommended, as it leads to 

 unfortunate multiplicity. He considers it proven that infection with 

 paratyphoid bacilli is often manifested by symptoms practically identical 

 with typhoid fever except for the Widal reaction, that there are differ- 

 ences (biological and in serum reactions) even among the paratyphoid 

 bacilli themselves (/9-paratyphoids), and that bacilli of the enteritidis 



1 Petruschky's bacillus fsecalis alcaligenus, while not an intermediate of the group (Durham), may 

 also produce typhoidal symptoms. 



