13 



dense clumps in marked and rapid manner (Bordet-Gruber 

 test in vitro), and in higher dilutions than other allied 

 microbes. 



Small doses of a recent culture of B. typhosus intraperi- 

 toneally injected cause death of guinea-pigs from acute 

 peritonitis in a short time, 20 to 36 hours, according to 

 size of dose, though it has to be remembered that when 

 subcutaneously injected it acts locally only, except very 

 virulent strains in fair doses produce sometimes general infec- 

 tion and death. The virulence differs with different strains ; 

 an animal previously prepared with subfatal doses of culture 

 of B. typhosus (of either living or dead culture) is immunised 

 and protected against an otherwise fatal intraperitoneal dose 

 of virulent B. typhosus, the animal in proportion to its 

 previous preparation suffers no ill effects, the peritoneally 

 injected bacilli rapidly undergoing granular degeneration 

 and change into granules and globules of dead matter 

 (Pfeiffer's phenomenon or test in corpore). Assuming that in 

 hanging drop and in staining a microbe shows the characters 

 above mentioned, produces in litmus milk acid but no coagu- 

 lation, gelatine streak and shake positive, neutral red negative, 

 in phenol broth or MacConkey fluid good growth, no indol 

 formation, in litmus lactose peptone negative, litmus bleached, 

 and further in Drigalski and Conradi plates, in Proskauer and 

 Capaldi medium I and II, in flagella stained specimens, and 

 in agglutination test in high dilution with typhoid serum (of 

 man, better of typhoid immunised animals), it answers 

 in positive fashion, we would consider these sufficient to 

 establish the identity of the microbe in question with the 

 B. typhosus. 



From the foregoing it will have been gathered that, in 

 order to definitely identify a particular microbe as the 

 B. typhosus, a number of tests, morphological, cultural and 

 experimental, have to be employed, and it will also be 

 readily understood that if in any material, subjected to 

 analysis, the typhoid bacillus should be associated with other 

 microbes belonging to the coli-typhoid group, the difficulty 

 of isolation of the B. typhosus out of the mixture must be 



