Inactivated Antisera: Precipitoids 93 



"antiprecipitin 1 " in inactivated serum acts upon the precipitins as Pick 

 supposed, for mixed active and inactive serum allowed to stand for 

 10 hours at 37 C. gave a precipitum on being added to culture filtrate. 

 They conclude that heated serum retains its combining, but loses its 

 precipitating power, for the reason that it consists of (stable) combining 

 and (labile) precipitating groups. In other words, they agree with 

 Miiller and Eisenberg, as stated above. 



It was further found by Kraus and von Pirquet (p. 71) that an 

 excess of old cholera antiserum prevented precipitation in culture fil- 

 trates, as did the inactivated fresh antiserum. The combining groups 

 would therefore appear to outlast the precipitating groups in such 

 antisera when stored. It also appears evident that the combining 

 groups, or, as we shall term them precipitoids, acquire a greater affinity 

 for the precipitable substance than the remaining intact precipitin. 

 This is completely in accord with what has been observed with agglu- 

 tinins and agglutinoids by Eisenberg and Volk (see p. 49). The 

 breaking down of precipitin to precipitoid is comparable to the changes 

 undergone by toxin into toxoid as observed by Ehrlich. 



Michaelis (25, ix. 1902) inactivated antiserum for ox-serum globulin 

 by exposure to a temperature of 68 C. for 15 minutes. He does not 

 think the precipitin is converted into precipitoid, for the reason that 

 when the heated antiserum is added to precipitable substance it 

 retards but does not prevent the action of fresh antiserum. He con- 

 siders the preventive action as non-specific, but depending upon physical 

 causes, viz. the addition of neutral colloidal substance, for any other 

 dilution of albuminous substance will exert the same effect. This is 

 contradictory to the views previously expressed, where the authors 

 agreed that the action was specific, for inactivated normal rabbit serum 

 added under similar conditions to inactivated antiserum (also from 

 rabbits) did not prevent precipitation. Michaelis (p. 459) moreover 

 claims that heated antiserum markedly reinforces the action of a 

 minimal quantity of fresh antiserum, as much as if one had added the 

 corresponding amount of fresh antiserum. These results require con- 

 firmation and suggest, it seems to me, that he may have worked with 

 incompletely inactivated antisera. Michaelis believes that precipitation 

 is not due to a single substance, the "precipitin," but to a complex 

 similar to that possessed by the haemolysins. With precipitins we 

 have the conjoint action of two substances, both absent in normal sera, 



1 Evidently a misnomer, precipitoid is a more suitable term. 



