398 CHOLERA 



is readily intelligible if we regard the subsequent immunity as 

 being a condition in which the body, having been once trained to 

 do so, readily manufactures antibodies and other protective sub- 

 stances when infection occurs. Since no protective substances 

 are present at the time, infection occurs as in a normal person, 

 but the defensive substances are very quickly produced. Shiga's 

 vaccine was prepared by emulsifying a twenty-four-hour agar 

 culture of the bacillus in 5 c.c. of normal saline, heating to 60 C. 

 for one hour, and submitting the dead bacilli to autolysis at 37 C. 

 for two days. It is then filtered and used in doses of 0^05 to 0-5 c.c. 

 The serum becomes strongly agglutinating and bactericidal. 

 Other methods have been proposed. 



Immunity reactions, especially that of agglutination, are of 

 great value in the diagnosis of dysentery, and especially of the 

 type of the bacillus present. In acute cases this is hardly 

 necessary, since modern methods have rendered the task of 

 isolating the bacilli from the stools an easy one. In the chronic 

 forms this is extremely difficult, and recourse must be had to the 

 agglutination test. The reaction is not as strong as in typhoid 

 fever, a positive result at a dilution of i : 50 being diagnostic. 

 The blood should be tested against any strains of dysentery 

 bacilli which may be available, especially if vaccine treatment is 

 to be used. 



The method of absorption of complement has also been used. 



Cholera. 



In cholera the living organisms are strictly limited to the 

 intestinal contents, and the disease appears to be a pure intoxica- 

 tion, without access of living bacteria to the tissues. It is, how- 

 ever, probable that this is not the case, and that the vibrios enter 

 the blood and there suffer rapid and complete bacteriolysis, their 

 endotoxins being liberated in the process. But there is nothing 

 that can be called a local lesion, and the disease is not a septi- 

 caemia in the ordinary sense of the word. 



The toxin of cholera is a typical endotoxin. The filtrates from 

 broth cultures are of very feeble toxicity, though they possess 

 immunizing properties, due doubtless to some degree of autolysis 

 which has taken place, and to the presence of free receptors. 

 Bacilli killed with agents such as chloroform or thymol are highly 

 toxic, especially if injected along with an immune serum, so that 

 they can be rapidly dissolved. The endotoxin can be prepared 



