XI] BACILLI : SPECIFICALLY PATHOGENIC 241 



that the normal habitat of the typhoid bacillus is the 

 circulating blood, hence its passage into the urine already 

 in the early phases of the disease. Dr. Horton Smith, 

 working in my laboratory, has paid special attention to this 

 question, and his conclusions do not confirm those arlrived 

 at by Wright and Semple. The identification of the typhoid 

 bacillus in the stools, in the urine, in the spleen, in the 

 blood, or in the glands, &c , if it is to be considered free 

 from criticism, must not content itself merely with the 

 demonstration of a general similarity as to size, shape, and 

 motility, or as to the general aspect of the plate cultiva- 

 tion, streak and stab cultures on Agar and in gelatine — it 

 is precisely on account of such general observations that 

 many of the statements made in previous years as to the 

 occurrence of the typhoid bacilli in one or the other tissue, 

 in one or the other locality, cannot be accepted as proven. 

 The identification of a bacillus as typhoid bacillus must be 

 such as to show that as regards every one and all of the 

 following characters there is complete harmony between it 

 and the bacillus obtainable in pure culture from the typical 

 spleen of a typical case of typhoid fever. The characters 

 are these : — ■ 



1. The typhoid microbe taken from the spleen of a 

 typhoid case is a cylindrical bacillus measuring on the 

 average 2-4 /x, in length ; in gelatine or Agar cultures already 

 after twenty-four hours there are present longer forms, some 

 filamentous ; the great majority of the bacilli from a recent 

 culture are distinctly longer and more cylindrical than those 

 of a similar culture of the typical bacillus coli. 



2. Examined in the hanging drop in sterile broth the 

 typhoid bacillus of a recent gelatine or Agar culture (16-24 

 hours old) is extremely motile, contrasting markedly with 

 a similar culture of the typical bacillus coli. 



