RELATIONSHIP OF BACILLUS TO DISEASE 379 



typhoid bacillus, and after the usual incubation period have 

 developed typhoid fever. Several cases of this kind have been 

 brought to our notice, and are not, we think, vitiated by the fact 

 that other similar instances have occurred without the subsequent 

 development of illness. These latter would be accounted for by 

 a low degree of susceptibility on the part of the individual or to 

 a want of pathogenicity in the cultures. 



As there is thus strong evidence of the etiological relationship 

 of the typhoid bacillus to typhoid fever, the view of the develop- 

 ment of the disease usually taken has been that the bacilli, 

 being ingested, multiply in the intestinal tract, cause inflamma- 

 tion and necrosis of the lymphoid tissue, and, gaining an 

 entrance to the general circulation, produce the septicsemic 

 phenomena which we have described. 



Within recent years, considerable attention has been attracted to 

 another view of the course of infection put forward by Forster and his 

 co-workers in Strasburg. According to this, the process is primarily a 

 septicaemia, and the intestinal manifestations are looked 'on as secondary. 

 The bacilli are supposed to gain entrance to the circulation possibly 

 through the tonsils, sore throat being a not uncommon initial symptom 

 of typhoid fever. In the blood they multiply, and, passing through the 

 liver, gain access to the gall-bladder, set up a catarrhal inflammation 

 there on the products of which they flourish, and thence pass out to 

 infect the intestine. The intestinal lesions are either due to an elective 

 action of bacteria brought by the blood, or come from infection by the 

 bacilli which pass out from the gall-bladder, the former being appar- 

 ently the alternative to which Forster leans. The evidence on which 

 this view is based consists, firstly, in the results of animal experiments 

 in which bacilli introduced intravenously have been subsequently found 

 chiefly or solely in the gall-bladder, it may be, persisting there for 

 weeks. Further, it is stated that bacilli can be isolated from the blood 

 during the later parts of the incubation stage of the disease, and before 

 they can be demonstrated in the intestine, where they are said not to 

 appear until sometime during the first week of active disease. And again 

 it is stated that in the bodies of persons dying from typhoid fever, while 

 bacilli are always present in the gall-bladder and in the upper parts of 

 the small intestine, they are frequently absent from the lower part of the 

 latter and from the colon. It cannot be said that this view of the 

 disease has been satisfactorily established. Opinion differs as to the 

 alleged late appearance of the bacilli in the intestine, and the infectivity 

 noticed during the incubation stage must be explained. Further, there 

 is strong reason for believing that multiplication of the bacilli in the 

 intestine can take place. The evidence of this rests on the finding of 

 bacilli, it may be in considerable numbers, in the faeces and even in the 

 blood of healthy individuals who have merely been in contact with 

 typhoid cases or typhoid carriers, and who show no symptoms of the 

 dis 



There is evidence that certain individuals are relatively insus- 

 ceptible to typhoid fever. The cases of the occurrence of 



