126 CLASSIFICATION OF INFECTIOUS DISEASES 



or less long and in which the pathologic manifestations are 

 anaphylactic in nature. 



The characters of the subgroups and species will be deter- 

 mined by the affinities of antigens for different tissues as 

 well as by the nature and properties of antibodies and the 

 role of these latter in the life of the sensitive cells. Thus, for 

 example, tuberculosis, glanders and leprosy on the one hand ; 

 syphilis, trypanosomiasis, relapsing fever and malaria on the 

 other hand form two closely allied groups of diseases. As 

 common characteristics they have the physicochemical 

 properties of their antigens and the nature of their anti- 

 bodies. In both groups immunity and anaphylaxis persist 

 only as long as the infection itself. The quantity of antibody 

 produced in excess is relatively very small and the sensitive 

 cells cease to produce it immediately after the disappearance 

 of the infecting bacteria. On the other hand the bacteria 

 seem to adapt themselves very easily to the medium of the 

 infecting organism and may live in it for years or even dozens 

 of years. This facility of adaptation on the one hand, 

 determines the more or less regular cyclic evolution of these 

 diseases whose mechanism has been the object of the very 

 interesting study of nagana in the guinea-pig by Levaditi 

 and Mutermilch. 



Typhoid and paratyphoid fever, plague, eruptive fevers, 

 yellow fevers, the hemorrhagic septicemia in animals, bovine 

 plague, the horse sickness of South Africa form another 

 group of diseases which are related to the preceding group 

 by the physicochemical properties of their antigens as well 

 as by the pathogenic properties of the compounds of these 

 antigens with antibodies in excess. This second group 

 differs from the first by the nature and origin of the anti- 

 bodies which sensitive cells produce in relatively large 

 quantities and reproduce for a long time after recovery from 

 the disease. In these cases acquired immunity-anaphylaxis 

 may persist for several years. 



Gonorrhea, influenza, aphthous fever form still another 

 group which is related to the type of tuberculosis by the intra- 

 cellular origin of the antibodies which determines the short 

 duration of immunity-anaphylaxis but differs fromjit by 



