IMMUNITY 199 



have a temperature as high as that of the chicken, can 

 be infected with anthrax without refrigerating. Behring 

 would ascribe the immunity of white rats to anthrax to 

 the high alkalinity of their blood, and claims to have shown 

 experimentally that a vegetable diet reduces this, and 

 fatigue is said to act similarly. 



In some cases the animal, after invasion by the organism, 

 becomes gradually tolerant to its presence (immunitas non 

 sterilisans). This is particularly the case in protozoan 

 infections, e.g. piroplasmosis. The animal, after a period 

 of ill-health, gradually recovers, though the organisms 

 may still be present, as can be demonstrated by injecting 

 some of its blood into a susceptible animal. Conceivably 

 the receptors necessary for the intoxication become 

 gradually used up, and when this state is attained the 

 animal becomes insusceptible. 



The blood, lymph, and other fluid and tissue juices 

 undoubtedly exert a more or less germicidal action on 

 bacteria experimentally in vitro, and to some extent 

 probably also in the body. But in this respect there is 

 often a marked difference between the circulating blood 

 and the blood in vitro. 



Lewis and Cunningham (1872), Traube and Gscheidlen 

 (1874), Fodor (1877), and Wysokowicz showed that bac- 

 teria injected into the circulation rapidly disappear, and 

 were inclined to attribute this result to the bactericidal 

 properties of the blood. In the main, however, this dis- 

 appearance is due to lodgment in the capillaries, phago- 

 cytosis, and excretion by the excretory glands. 



Halliburton prepared from the lymphatic glands a 

 protein, cell-globulin /3 (really a nucleo-protein). Hankin 

 found that this substance had marked germicidal properties, 

 and concluded that it was probably the germicidal con- 

 stituent of the blood-serum. Bitter, who repeated Hankin's 

 experiments, failed, however, to confirm them. To the 



