210 BACTERIOLOGY FOR NURSES 



cose, and mannite, but has no effect upon lactose or saccharose. 

 The identification of the organism is readily established by means 

 of the agglutination reaction. 



Resistance. Typhoid bacilli exhibit about the same degree 

 of resistance to heat as most non-spore-bearing organisms. They 

 are killed by exposure to a temperature of 56 C. in fifteen minutes. 

 Mercuric chloride 1 to 1000 destroys them in one to five minutes 

 and carbolic acid 1 to 100 in five to fifteen minutes. As a rule 

 they are less resistant to disinfectants than B. coli. Such substances, 

 however, as brilliant green and crystal violet inhibit the growth of 

 the latter without affecting the typhoid bacilli. Application has 

 been made of the fact in preparing special media for the isolation 

 of B. typhosus from feces. Since the organisms are rarely found 

 in nature it is difficult to determine the length of time they will 

 live outside of the body. In feces in privy vaults or on the ground 

 they tend to die out rapidly ; the majority may be dead within 

 twenty-four hours. Some, however, may persist for a much longer 

 period. According to certain authorities they may remain alive 

 in feces during the winter for five months. They have been re- 

 ported to remain alive in oysters for one month ; in water they 

 seldom live longer than seven days. Laboratory experiments 

 show that in ice the numbers rapidly decrease ; a certain percentage 

 may live for four months, but by the end of six months all are 

 killed. 



Pathogenesis. There is no evidence that the typhoid bacillus 

 is ever associated with any disease in animals nor is any disease 

 known amongst animals which in any way resembles typhoid 

 fever. Subcutaneous or intraperitoneal inoculations of pure 

 cultures produce a short, acute sickness which usually ends fatally 

 in from twenty-four to forty-eight hours, but which in no way 

 resembles the disease as it occurs in man. Attempts to produce 

 the disease by feeding animals on typhoid dejecta mixed with 

 their food have been equally unsuccessful except in the case of 

 anthropoid apes. 



In human infection inflammation and ulceration in the Peyer's 

 patches and solitary glands of the intestine are the characteristic 



