CHAPTER XV. 



THE APPLICATION OF IMMUNOLOGICAL 

 PRINCIPLES TO DIAGNOSIS. 



WHILE in the foregoing chapters we have been interested largely 

 in the reaction of the animal body to the introduction of alien cells 

 and cell products, from the standpoint of therapy, it is important 

 to note that some of the principles involved in these reactions have 

 also found application in the diagnosis of many of the infectious 

 diseases. The recognition of the formation of agglutinins has thus 

 led to the discovery of the most important method in the diagnosis 

 of typhoid fever, paratyphoid fever, and Malta fever; the principle 

 underlying the formation of bacteriolysins is utilized in the diagnosis 

 of cholera; the formation of special antibodies, which in the presence 

 of corresponding antigen absorb complement, and which may thus 

 be recognized indirectly by the demonstration of such complement 

 fixation, serve as a basis of the Wassermann diagnosis of syphilis; 

 the recognition of the general allergic state in the sense of v. Pirquet 

 has led to some of the most^ important methods in the diagnosis of 

 tuberculosis and syphilis; the precipitins play an important role in 

 the recognition of specific albumins, and serve as a basis of the 

 modern tests for blood in legal medicine; the formation of anti- 

 ferments has been utilized in the diagnosis of cancer, etc. 



^Yhile a detailed account of all the immunological methods of 

 diagnosis would lead us too far, and would indeed furnish sufficient 

 material for a special volume, it may not be out of place to consider 

 a few of the more important methods of this order in some detail. 



THE AGGLUTINATION REACTION. 



In 1896 Griiber and Durham pointed out that the addition of 

 cholera and colon immune serum to bouillon cultures of the corre- 

 sponding organisms produced a remarkable effect, for on standing 

 for a number of hours the turbidity of the cultures disappeared; 



