INFECTIONS OF THE DIGESTIVE TRACT 167 



Paratyphoid and Allied Infections. By means of 

 careful biochemical studies, including especially the study 

 of the fermentative action on sugars (first systematically 

 employed by Professor Theobald Smith *) and the agglu- 

 tination reactions and pathogenic properties, it has been 

 found that there is an important group of pathological 

 bacteria which according to their characters range them- 

 selves between the group of colon bacilli and the typhoid 

 bacilli. The group is large and somewhat heterogeneous 

 as regards certain properties, such- as agglutinative be- 

 havior and pathogenic qualities. The group includes 

 the inciters of hog-cholera, 2 of the spermophile disease, 

 of mouse typhoid, of guinea-pig disease, of certain forms 

 of pseudo-tuberculosis, of calves' diarrhoea, of psittacosis 

 or parrot plague (which may cause an atypical pneu- 

 monia in man), and it includes the paracolon and para- 

 typhoid bacilli, B. enteritidis and Sanarelli's bacillus of 

 yellow fever. 3 A glance at this somewhat formidable 

 list shows that many of the bacteria in question are the 



Gahrungskolbchen in der Bakteriologie," Centralbl. 

 f. Bakt., vii, p. 504, 1890; "Zur Unterscheidung zwischen Typhus- 

 und Kolonbacillen," ibid., xi, p. 367, 1892. 



2 The agglutinative characters of some of the bacteria in this 

 group are very similar though probably not really identical. 

 Thus Smith found the agglutinative behavior of certain hog- 

 cholera bacilli to be indistinguishable from that of Sanarelli's 

 bacilli of yellow fever. It is possible that common group agglu- 

 tinins were so abundant in the sera used as to mask the action of 

 very specific agglutinins that may have been present. 



3 Another group of aberrant colon-like bacilli includes the spe- 

 cific incitants of various infectious diseases of wild and domestic 

 birds. These organisms retain the ability to coagulate milk and 

 make indol, but differ from colon bacilli in showing weakened 

 fermentative powers. 



