94 The Nature of Precipitin Reactions 



in contrast to what is the case with the haemolysins. In the haemato- 

 sera then there are two substances, the thermolabile being predominant, 

 the thermostable being small in amount. 



Referring to the neutralizing action of inactivated precipitating 

 antisera as observed by Mtiller, Eisenberg, Kraus and von Pirquet, 

 above described, I would add that an analogous phenomenon has also 

 been observed with regard to specific bacteriolytic sera by Neisser and 

 Wechsberg, Lipstein, and Walker (see Bacteriolysins, p. 21), the inacti- 

 vated bacteriolytic serum, containing an immune body, which antagonizes 

 the action of fresh antiserum, when it is added to the latter in excess. 



The Non-reactivatability of Heated Precipitating Antisera. 



In the paper by Myers (14, vn. 1900) that author stated that he 

 had succeeded in obtaining an antiserum for Witte's pepton, that he 

 had been able to inactivate it by heat (see p. 112) and to reactivate it 

 with normal rabbit serum. His observations in this regard have not 

 been confirmed, although he was the first to refer to inactivated pre- 

 cipitin as precipitoid, drawing an analogy between the change observed 

 in precipitin with that which takes place when toxin is converted into 

 toxoid. If Myers' observations were correct, then precipitins would 

 constitute receptors of the third order (see p. 12) according to Ehrlich. 



No observer has been able to reactivate precipitating antisera since 

 Myers. Attempts have been made by Eisenberg (v. 1902, p. 302), 

 Kraus and von Pirquet (5, vn. 1902, p. 68), Michaelis (9, x. 1902, 

 p. 734), and myself. Since the addition of a complement to inactivated 

 antisera does not reactivate them, we must conclude in the light of 

 Ehrlich's theory that the precipitins constitute receptors of the second 

 order (see fig. 2, p. 12), as is assumed to be the case with toxins and 

 agglutiriins. In Eisenberg's experiments (p. 297) the antiserum was 

 inactivated by an exposure of 1 hour to 72 C., reactivation being 

 attempted both with homologous and heterologous sera, and also by 

 adding quantities of active antiserum, too small to produce by them- 

 selves any reaction. 



On Immune Bodies in Precipitating Antisera. 



Until 1902 immune bodies had only been observed and studied in 

 sera which act on formed elements, bacteria or different cells. Gengou 

 (25, X. 1902, p. 739) has sought for them in precipitating antisera (from 

 rabbits) for milk, egg-albumen, horse fibrinogen, and also in the antiserum 



