TYPHOID FEVER. 179 



therefore be finally reached only when, after comparison with 

 an unequivocal pure culture (from the spleen of a typhoid 

 patient), all doubt has been removed that both the culture 

 obtained from the water and the earlier pure culture agree 

 in every detail, and with regard to both PfeifTer's and 

 Gruber's reactions. Notwithstanding these difficulties, 

 typhoid-bacilli have been demonstrated in drinking-water 

 in several instances by competent observers. 



The prophylaxis of typhoid fever, in accordance with 

 what has already been said, consists especially in the anti- 

 sepsis of the sick-room. The feces and the urine from 

 typhoid patients, all materials contaminated by these dis- 

 charges (body-clothing and bed-clothing, etc.), in fact, 

 everything that has come in contact with the patient, must 

 be most thoroughly disinfected, as the adherent bacilli may 

 constitute the source of new infections. Methods of dis- 

 infection are described in the Appendix. 



In the second place, the prophylaxis concerns itself prin- 

 cipally with the hygienic relations of the drinking-water, 

 which must be boiled before being used whenever suspicion 

 of contamination exists in times of epidemics. 



Immunity and Cure. Typhoid fever is one of those dis- 

 eases, as shown by clinical experience, that attack the same 

 individual but once. Two attacks have occurred in the 

 same individual in about two per cent, of all the cases ; 

 the occurrence of three attacks in the same individual has, 

 according to a recent report, been observed only five times, 

 and four attacks in the same individual but once. It 

 may, therefore, be concluded that recovery from an attack 

 of typhoid fever confers a certain degree of immunity. Sup- 

 port for this view is found in the fact that the blood-serum of 

 some individuals who have recovered from typhoid fever 

 exhibits immunizing properties with relation to the disease 

 induced experimentally in animals with typhoid-bacilli. 



The immunization of animals to typhoid-bacilli is readily 

 effected. Bouillon-cultures heated to a temperature of 60 C. 

 (140 R), or agar-cultures exposed to a temperature of from 

 54 C. (129.2 F.) to 56 C. (132.8 F.) have" been employed 

 for this purpose, and also the filtrate of unheated virulent 

 cultures, or of cultures in thymus-bouillon.* The simplest 



* According to a recent communication, Buchner and Hahn obtained im- 

 munity with the cell -juice of typhoid-bacteria rubbed up and expressed by the 

 method of E. Buchner (p. 32). (The plasmatic cell-juices of the bacteria 



