820 AGGLUTININS AND THEIR APPLICATIONS 



micro-organism should be determined for each serum.' One and one-half to three 

 times this dose is generally found satisfactory for use in absorption experiments. The 

 time and temperature at which absorption is carried out are of importance. Two hours 

 at 50° C. is adequate. It is obvious that the carrying out of an absorption experiment 

 must be controlled by a tube containing serum alone, diluted to the same degree as 

 the absorbing mixtures and subjected to the same physical conditions. 



RECIPROCAL ABSORPTION OF AGGLUTININS 



It is fallacious to assume the identity of two micro-organisms A and B if the 

 agglutinins of A serum are exhausted (or nearly so) by B bacteria, though for practical 

 purposes this assumption is sometimes justifiable. It is absolutely essential in order to 

 establish complete identity that the serum of A be exhausted for agglutinins of A by 

 the suspension of B, and that the serum of B be in like manner exhausted for agglu- 

 tinins of B by the suspension of A. This procedure is termed "reciprocal absorption." 

 In the ultimate analysis there is no more accurate means of species identification than 

 this method when properly carried out and adequately controlled. White, Krum- 

 wiede, and others have particularly stressed the importance of reciprocal agglutina- 

 tion as the only legitimate use of the phenomenon of agglutination absorption for 

 establishing the identity of culturally similar species. To quote White: "Any other 

 mode of applying the absorption test to the proof of identity is worse than futile."^ 



GROUP AGGLUTININS 



Andrewes^ has brought forward interesting data bearing on the problem of group 

 agglutination among the Salmonella. He attempted an analysis of the antigens in the 

 bacteria and of their agglutinins in their respective sera. "Single colony broth cultures 

 picked from a plating of a stock culture do not all behave in an antigenically similar 

 manner. In all mass cultures there exist side by side two types of bacilli, and two 

 only, sharply differentiated in their antigenic structure. The one contains the specific 

 antigen and the other the group antigen, but .... neither is absolutely pure." It 

 was found impossible to cultivate these as separate entities; each changes readily into 

 the other; they are not identical with the "rough" and "smooth" colonies of Ark- 

 wright, later to be mentioned. By carefully selecting, the specific type antigens and 

 producing with these specific sera, Andrewes suggests that the absorption test may 

 be eliminated. He further claims that by using formalinized emulsioijs of specific type 

 the sharpness and value of serodiagnosis in human infection would be enhanced. 

 Krumwiede^ points out the limitation of Andrewes' method as a substitute for ab- 

 sorption. 



FURTHER APPLICATIONS OF THE AGGLUTINATION REACTION 



The application of the reaction of agglutination may conveniently be grouped in 

 three categories, namely: identification of micro-organisms, examination of sera, 

 standardization of sera and vaccines. Specific allusion to some of its uses has already 



' Krumwiede, C, Cooper, G., and Provost, D. J.: J . Immunol., 10, 55. 1925. 



2 White, P. B.: "Medical Research Council, Spec. Rep. Series," No. 91, p. 12. 1925. 



3 Andrewes, F. W.: op. cit., 25, 506. 1922. 



4 Krumwiede, C, Cooper, G., and Provost, D. J.: he. cit. 



