442 STUDIES IN IMMUNITY. 



but by properties of adhesion, have been very instructive. The 

 agglutination and hemolysis of red blood cells by barium sulphate 

 (Gengou), by silicic acid (Landsteiner and Jagic), and similar facts 

 brought out by researches of many writers on colloids, gave greater 

 and greater importance to the effect of adhesion in the reactions 

 between antisera and their antigens. 



In hemolysis in particular, the phenomenon of alexin absorption 

 by corpuscles laden with sensitizer (amboceptor) has given rise to 

 most active controversies. The sensitizing theory of Bordet consists 

 essentially in the conception that the sensitizer, which possesses in 

 itself no particular affinity for the alexin, forms, by uniting with 

 certain substances in the corpuscle, a complex endov/ed with prop- 

 erties of molecular adhesion for the alexin which are not possessed 

 by the normal corpuscle. The corpuscle that has been modified in 

 this manner would seem to acquire the property of adsorbing alexin, 

 of manifesting an avidity which may be compared to that which 

 occurs in the fixation of fibrinogen or other albuminous substances 

 by chemically inert particles (for example, barium sulphate) or to 

 the union of diphtheria toxin with precipitates of calcium, etc. As 

 we know, this point of view differs from the amboceptor theory of 

 Ehrlich, in accordance with which this antibody owes its interme- 

 diary function to the fact that it possesses in its molecule two com- 

 bining atom groups: one(complementophilic), which unites with the 

 alexin, and the other (cytophilic), which combines with the corpus- 

 cle. We shall not take up at this point a general discussion of these 

 theories, which one of us in collaboration with Dr. Gay has recently 

 considered ; * we may recall that no experiment has ever shown 

 that sensitizers can unite with alexin in absence of antigens. Such 

 a combination under certain conditions has been asserted by Ehrlich 

 and Sachs, t as a result of their researches on the hemolysis of guinea- 

 pig corpuscles by horse serum to which bovine serum has been 

 added. 



Bordet and Gay t undertook two years ago the study of this in- 

 stance of hemolysis and arrived at the conclusion that Ehrlich and 

 Sachs' interpretation is inexact. Their conclusion, in turn, has 



* See p. 398. 



t See Studies on Immunity, Ehrlich-Bolduan, Wiley & Co., p. 209. 



t See p. 363. 



