108 THE SIDE-CHAIN THEORY 



antibodies. If washed red corpuscles are thus brought together with 

 a corresponding hemolytic amboceptor and are incubated at body 

 temperature, the amboceptor is anchored to the corpuscles and can 

 no longer be removed by washing. That an interaction has actually 

 taken place may be shown by adding fresh complement, when hemo- 

 lysis will promptly occur. Analogous results are obtained with the 

 bacteriolytic amboceptors, agglutinins, and precipitins, and as in the 

 case of the antitoxins it may here also be shown that no destruction 

 of the antigen takes place. If milk and a corresponding precipitin 

 (lactoserum) are thus brought together, a precipitate of antibody 

 casein is formed, and if this is boiled, after careful washing in normal 

 salt solution, the precipitate dissolves, and in the resulting solution 

 unchanged casein can be demonstrated, which may in turn be 

 precipitated by the addition of a new portion of antiserum. The 

 precipitin can similarly be recovered by treating the precipitate 

 with T "Q- sodium hydrate or sulphuric acid. 



While a destructive action on the part of the antibody upon the 

 antigen can thus be excluded, the latter may be destroyed secondarily 

 in consequence of the activity of some additional factor. This 

 actually takes place when complement acts upon cells that have 

 been brought together with corresponding cytotoxic (lytic) ambo- 

 ceptors. The term lysin, of course, suggests that it is the amboceptor 

 that is lytic, but it should not be forgotten that the lytic effect only 

 occurs when complement is present, that the latter really is the lytic 

 agent, and that the amboceptor itself produces no appreciable effect 

 upon the antigenic cells. 



Chemical Nature of Antigen-antibody Interaction. The assump- 

 tion that the interaction between antigens and antibodies is of 

 a chemical nature carries with it the inference that the reacting 

 substances must combine with one another in certain definite 

 proportions or multiples thereof, viz., that if one unit of anti- 

 toxin will neutralize one unit of toxin, ten units of the one should 

 combine with ten of the other, twenty with twenty, etc. The inves- 

 tigation of this particular side of the problem has led to a great deal 

 of controversy arising from erroneous interpretations of various obser- 

 vations, owing to imperfections in technique, lack of knowledge of 

 detail, etc., and has consequently been productive of an enormous 

 amount of labor, for much of which we are indebted to Ehrlich and 

 his school. 



