THE PARATYPHOID BACILLI 421 



of the bacteriological characteristics of the typhoid and colon bacilli and which 

 give rise to a clinical disease having all the symptoms of enteric fever. 



Further study however soon revealed the fact that these paratyphoid bacilli 

 were, at all events in the laboratory, very closely related to if not identical 

 with organisms which had been isolated from certain septicaemic diseases in 

 animals accompanied by haemorrhages the hsemorrhagic septicaemia group. 

 The first of this group to be described was that isolated by Salmon and 

 Theobald Smith in 1885 from swine suffering from hog-cholera and known as 

 the bacillus of hog-cholera. 1 



The paratyphoid bacilli especially the B variety, had also many charac- 

 teristics in common with an organism isolated by Gaertner in 1888 at Franken- 

 hausen from an epidemic of food-poisoning, and known as the bacillus 

 enteritidis Gaertner. 



Closely related also to the paratyphoid bacilli is an organism known as 

 the bacillus enteritidis Aertrycke, 2 isolated in 1898 by de Nobele from an 

 epidemic of food-poisoning at Aertrycke in Belgium and by Durham at 

 Hatton in England. By its cultural characteristics this organism cannot be 

 distinguished from the bacillus enteritidis Gaertner? but as Durham showed 

 by an application of the agglutination reaction, then recently introduced, 

 the two could be sharply differentiated . 



Hence in the first quinquennium of the century a number of organisms 

 were known which from the laboratory point of view were all very like each 

 other, but which and this seemed remarkable gave rise to different dis- 

 eases. The paratyphoid bacilli A and B caused a septicaemic disease clinically 

 almost if not quite identical with enteric fever ; the haemorrhagic septicaemia 

 group caused a septicaemia and diarrhoea in animals ; while the group consist- 

 ing of Gaertner's and Durham's and de Nobele's bacilli were and still are 

 regarded as the cause of epidemics of food-poisoning. 



It was easy to distinguish the paratyphoid A bacillus from the other bacilli 

 mentioned both by its cultural characteristics and by its agglutination 

 reactions. The gaertner bacillus also could by its agglutination reactions 

 be distinguished from the aertrycke bacillus, the bacillus of hog-cholera and 

 the bacillus paratyphoid B. 



Then difficulties arose as to the nature of the three last-named organisms. 

 The bacillus of hog-cholera was soon shown to be identical with the aertrycke 

 bacillus ; and the relationship of the latter bacillus to the paratyphoid 

 B bacillus therefore alone remained to be determined. The position in 1906 

 was summarized by Boycott : " On the whole, the distinction between 

 hog-cholera [aertrycke] and paratyphoid B, though slender, seems to be 

 real. The morbific relations to man are different, for while the former gives 

 rise to a sudden acute illness (food-poisoning), paratyphoid B causes a disease 

 with no clear clinical distinctions from enteric fever." 4 



With a view to studying Castellani's absorption reaction Bainbridge took 

 the paratyphoid bacilli as a suitable group upon which to work. By the 

 aid of this reaction he has now made it clear that the bacillus paratyphoid B 



1 At the time, these authorities believed the organism to be the cause of hog-cholera 

 and their opinion was accepted by other observers subsequently. Hence the name by 

 which it is still very commonly known, the bacillus of hog-cholera, bacillus suipestifer, or 

 bacillus cholerce suis. In 1903 however the researches of de Schweintz, Dorset and others 

 showed that hog-cholera is not to be ascribed to the Salmon-Smith bacillus but to a 

 filter-passing organism (Chap. LXIV.), the hog-cholera bacillus being merely a secondary 

 infection. 



2 This bacillus will in future be described as " the aertrycke bacillus." 



3 In future referred to as '' the gaertner bacillus." 



4 See however Paratyphoid B as a cause of food -poisoning p. 432. 



