HISTORIC 



267 



species, the cultures would lose their turbidity, flake-like clumps would 

 form and sink to the bottom of the tube, and the supernatant fluid 

 would become clear. Gruber at the same time called attention to the 

 fact that agglutinins were not absolutely specific for their own antigen, 

 but would agglutinate, to a lesser extent, closely allied species of bacteria. 

 In 1896 Pfaundler drew attention to a peculiar phenomenon ob- 

 served when bacteria were grown in an immune serum. Long and more 

 or less interlaced threads of bacteria developed, which were regarded as 

 due to agglutinins. At that time considerable emphasis was laid upon 

 the importance of Pfaundler's reaction, but at present the ordinary 



FIG. 75. THEORETIC FORMATION OF AGGLUTININS. 



agglutination tests have superseded this reaction as a practical diag- 

 nostic procedure. 



In 1896 Widal and Griinbaum first turned these facts to practical 

 use in the diagnosis of typhoid fever. These investigators found that 

 the serum of patients suffering from typhoid fever acquires a high agglu- 

 tinating power for Bacillus typhosus, and since this phenomenon gen- 

 erally manifests itself comparatively early in the disease, its recognition 

 has considerable diagnostic importance. It is purely accidental that 

 we speak of the " Widal reaction" in typhoid fever, rather than of the 

 "Grunbaum reaction," for the latter observer conducted similar studies 



