IMMUNIZATION 159 



the patient retained a content of agglutinin in his 

 blood, reaching 20 units seven and a half years 

 after his illness (Malta fever). Different patients 

 show in this respect a high degree of individuality. 

 In most cases the agglutinin has disappeared after 

 two years or is only present in very small quantities. 



The presence of agglutinins in the blood during 

 and after diseases is of a high diagnostic value 

 (Reaction of Gruber - Vidal). It is very well 

 known that after some diseases, such as scarlatina, 

 measles, and whooping-cough, the immunity against 

 these diseases lasts for the whole life. It is not 

 clear whether this peculiarity depends upon a small 

 content of antibodies remaining for a long time in 

 the tissues of the patients. 



But it seems to me in any case that the study 

 of the active immunity throws much light on the 

 progress of illnesses produced by micro-organisms. 

 It is a very promising feature that we are able to 

 treat the content of antibodies during and after 

 the illness in a strictly quantitative manner, and that 

 we have succeeded in subjecting this extremely 

 important phenomenon to calculations which agree 

 as well with the observed facts as with ideas 

 conceived for the explanation of other parts of 

 chemical science. 



