354 A MANUAL OF BACTERIOLOGY 



almost invisible. If, however, the reaction of the potato is 

 neutral or alkaline, the growth may be yellowish. The 

 B. typhosus grows well in milk, with slight permanent 

 acidity, but without coagulation. 



Acid is formed in small quantity during its growth in 

 many media (volatile fatty acids, and lactic acid), which 

 can be demonstrated by cultivating in litmus milk, or in 

 litmus glucose media, and the organism will grow in slightly 

 acid media. Neither gas nor indole 1 is formed in cultures ; 

 acid is produced from glucose, but no gas ; lactose is 

 unacted upon. The fermentation reactions on various 

 media are given in the Table on p. 381, and are there con- 

 trasted with those of the B. coli and other organisms (see 

 also p. 384). Chatterjee 2 finds that agar on which the 

 typhoid bacillus has been grown contains substances which 

 inhibit further development of the organism if it be inocu- 

 lated on to an agar culture which has been scraped so as 

 to remove all growth. 



Pathogenicity. In cases of typhoid fever in man the 

 Bacillus typhosus is widely distributed in the body, in the 

 various tissues, and in the blood, from which it may be 

 obtained by cultivations made from at least 0-5 c.c. (see 

 " Clinical Diagnosis," p. 369). The bacillus is constantly 

 present in the blood from the commencement of the disease, 

 though not in large numbers, and cultures from the blood 

 in competent hands result in the recovery of the organism 

 in approximately 100 per cent, of the cases ; in the later 

 stages of the disease it is less frequently recovered. 3 In 

 addition to being present in the Peyer's patches, mesenteric 

 glands, and spleen, the B. typhosus has been found in the 

 rose-spots of the eruption, in the sweat, in the sputum 



1 Occasionally a feeble indole reaction may be obtained by careful 

 testing. 



2 Trans. Fourteenth Internal. Cong, of Hygiene (Berlin, 1907), Bd. iv, 

 p. 34. 



3 Coleman and Buxton, Amer. Journ. Med. Sci., June 1907. 



