170 



ANAPHYLAXIS IN ITS RELATION TO DISEASE! 



place, and becomes, in turn, to a certain extent at least, responsible 

 for the more or less continuous symptomatic evidence of disease. 

 If the number of organisms is small, or if they have been attenu- 

 ated by artificial means, the incubation period is much longer. In 

 such an event the antibody production begins in the third week, 

 but it is not until the fifth week that a sufficient quantity of ana- 

 phylatoxin is formed to elicit manifest symptoms (Fig. 7). 



Days ( 1 



Threshold of Death- 



Injection of virulent 

 | tubercle bacilli 



Manifestations of Disease 



Diagram illustrating the interaction between antigen and antibody in a fatal case of cattle 

 tuberculosis, following the injection of a moderate dose of tubercle bacilli. (Taken from v. Pirquet.) 



FIG. 7 

 15 



I Infect ion 



Threshold of clinical evidence of disease I 



Diagram illustrating a protracted period of incubation in its relation to the interaction between 

 tubercular antigen and the corresponding antibody; infection having been produced by the admin- 

 istration of tubercle bacilli in small number or in attenuated condition. (Taken from v. Pirquet.) 



The subsequent course of the infection will, of course, depend 

 upon circumstances. If recovery takes place the further multipli- 

 cation of tubercle bacilli ceases; the foci that are already in exist- 

 ence are encapsulated and the active clinical symptoms disappear. 



