478 



INFECTION AND IMMUNITY. 



of living cultures Kolle has proposed the use of 

 virulent cultures which have been killed by expo- 

 sure to a temperature of 58 C. for one hour. The 

 vaccine is preserved by the addition of 0.5 per 

 cent, phenol. In the Japanese epidemic of 1902 

 this method was used on an extensive scale. The 

 incidence of disease among the uninoculated was 

 13 per cent., among the inoculated 0.06 per cent. ; 

 the mortality among the uninoculated was 10 per 

 cent., among the inoculated only 0.02 per cent. 

 The disease, when it occurred in the inoculated, 

 was of a mild type. A single injection of from 2 

 to 4 mg. of a killed agar growth was given sub- 

 cutaneously (cited by Kolle). Strong has pro- 

 posed the use of the products of autolysis of the 

 cholera vibrio as a vaccinating substance, a method 

 founded on the observations of Neisser and Shiga 

 in relation to typhoid, and of Conradi and Drigal- 

 ski in relation to dysentery. The local and general 

 symptoms are said to be of a mild type. The 

 method has had no practical trial. 



Natural From what was said above in connection with 

 "ucep^ the so-called cholera carriers, it is evident that not 

 lity * all are equally susceptible to infection with chol- 

 era. In the few instances in which infection has 

 been attempted deliberately, some contracted the 

 disease, at least one case ending fatally, whereas in 

 others either a mild infection or none at all took 

 place. The conditions on which such cases of in- 

 dividual immunity depend are not known conclu- 

 sively, although it is often intimated in a general 

 way that a strong bactericidal power of the body 

 fluids, or a high phagocytic power on the part of 

 leucocytes, is responsible for it. The gastric juice, 

 on account of its acidity, offers a barrier to the 



