264 INFECTION AND RESISTANCE 



(agglutination) consists in the flocculation of large particles in sus- 

 pension the bacteria while in the other the precipitation is one 

 of smaller units the precipitable colloidal particles of the protein 

 solutions. This phase of the subject will be more thoroughly dis- 

 cussed directly. 



Meanwhile, it is noticeable also that, even without drawing the 

 physical parallel between the two reactions, there is much in the 

 behavior of the antibodies the agglutinins and the precipitins as 

 conceived by Ehrlich, which led him and his school to attribute to 

 them a similar receptor structure. Like the agglutinins, the pre- 

 cipitins are not inactivated by 56 C., but when once rendered in- 

 effectual by higher temperatures (70 C. or over) they can no longer 

 be reactivated by the addition of fresh normal serum. For this 

 reason chiefly Ehrlich has conceived that both agglutinins and pre- 

 cipitins are "haptines" of the second order. 



BACTERIAL 



CELL OR ^ (BODY CELL 



OTHER ANTIGEN 



SCHEMATIC REPRESENTATION OF EHRLICH 's VIEWS ON THE STRUCTURE OF PRE- 

 CIPITINS. 



Ehrlich assumes that when dissolved protein substances ordi- 

 narily suitable for body nutrition are injected into animals, they 

 become anchored to the cells by such receptors of the second order. 

 When overproduction occurs in response to repeated stimulation of 

 the cells by consecutive injections (see Side-Chain Theory), these 

 haptines of the second order circulate as agglutinins or pre- 

 cipitins. Since they act without the apparent cooperation of alexin, 

 he supposes that they carry within themselves the "zymophore," or 

 ferment groups, by means of which the agglutination or coagulation 

 is accomplished. It is this zymophore group which, it is assumed, 

 accomplishes the digestion of the foreign protein before its assimila- 

 tion, when these receptors are still parts of the living cell. 



Thus the conception of precipitins is identical with that formu- 

 lated by the same school concerning the agglutinins, and the deduc- 

 tions from these premises have been essentially similar. Thus, anal- 

 ogous to the conditions prevailing in agglutination, Pick, 42 and 

 Kraus and v. Pirquet 43 have shown that when precipitating serum 

 is inactivated by heat, and then is added to bacterial filtrates, it will 



42 Pick. "Hofmeister's Beitrage," Vol. 1, 1902. 



43 Kraus and von Pirquet. Centralbl. f. Bakt., Vol. 32, 1902. 



