798 



THE MECHANISM OF AGGLUTINATION 



It must be noted, however, as pointed out by Loeb, that the behavior of the coat- 

 ed particle may differ in some respects from that of the protective colloid. Collodion 

 particles, for instance, coated with native egg albumin precipitated at the isoelectric 

 point of egg albumin, whereas egg albumin itself does not precipitate under these con- 

 ditions. Loeb suggests that the protein is denatured by the formation of the film, as 

 has been shown to be the case at the air-liquid surface. 



io5 



20i7 3D?7 400 500 So5 TOO 

 Concentration-of-seram 



Fig. 9. — Effect of eleven specific agglutinating sera upon the potential and agglutination of their 

 homologous organisms. These experiments were done over a period of about two years and three 

 different cataphoretic cells were utilized in the work. All experiments in M/200 glycocoll-phosphate- 

 acetate buffer mixture, pH 7.0. 



The same point is brought out in the interesting observation of Shibley^ that all 

 organisms studied when treated with an excess of immune serum tend to reach the same 

 value of the potential, independent of the potential of the bacteria themselves. In some 

 cases it was found that the addition of the immune serum decreased and in others in- 

 creased the potential. Shibley's results are shown in Figures 9 and 10. They show 

 quite clearly that the sensitized bacteria behave in regard to both cataphoresis and 

 agglutination like particles of denatured globulin. 



In most cases Shibley found a marked effect of the immune serum on the poten- 

 tial of the bacteria, and this might be used as a diagnostic test, as Shibley suggests. 

 Mellon and his co-workers- were in fact able to detect a reaction between the anti- 

 body and the bacteria by cataphoresis measurements although the agglutination test 

 was negative. 



' Shibley, G.: J . Exper. Med., 40, 453. 1925; 44, 667, 1926; Tulloch, W. J.: Biochem. J., 8, 243. 

 1914, had suggested that sensitized bacteria were comparable to denatured proteins. 

 = Mellon, R. R., ct a!.: J, Immunol., 11, 161. 1926. 



