1907.] Phenomena exhibited by Precipitin Antisera. 467 



simple a statement. Thus a precipitin antiserum (No. 38) prepared with hen- 

 egg white, when heated to 70° C. for 30 minutes, did not become noticeably 

 inactive or inhibitory. When heated to 72° C. for 10 minutes, it was rendered 

 almost completely inactive, but not noticeably inhibitory. Exposure to 72° C. 

 for 30 minutes produced complete inactivation without, however, any 

 appreciable inhibition. Further exposure to 75° C. of a portion of the 

 antiserum already heated to 72° C. for 30 minutes yielded a solution still 

 wholly inactive, but now strongly inhibitory. We have repeated these 

 observations with concordant results. 



It is noteworthy that the conversion of antiserum from the active to the 

 inactive condition appears to be a temperature change rather than a time 

 effect, and that inactivation occurs rapidly at the temperature at which we 

 succeeded in obtaining, in an acidulated solution of a homologous antiserum, a 

 heat coagulum not found in natural rabbit serum.* 



A second means of effecting a separation of the phenomena of inactivation 

 and of inhibition was accidentally revealed. Another homologous antiserum 

 (No. 11), prepared in the rabbit by injections of hen- egg white, had been 

 stored in a dry condition. At the expiry of 11 months it was found to be 

 still readily soluble in salt solution, but to have become wholly inactive, no 

 trace of precipitate appearing on interaction with homologous protein. When 

 0*1 c.c. of this unheated inactive antiserum solutionf was allowed to interact 

 with an equal volume (0*1 c.c.) of active homologous antiserum (Nos. 23 and 25 

 were separately employed) and with homologous protein, no appreciable 

 inhibition could be detected. When, however, a triple volume (0'3 c.c.) of the 

 inactive antiserum solution interacted with a single volume (01 c.c.) of the 

 active antiserum in otherwise similar circumstances, the full precipitate was 

 in every instance obtained, but in three out of six tubes its appearance was 

 delayed for about 24 hours. When it is borne in mind that three volumes 

 (0*3 c.c.) of any antiserum heated to 75° C. was invariably found to completely 

 inhibit precipitation when one volume (0*1 c.c.) of a different but homologous 

 antiserum interacted with homologous protein, it must be admitted that any 

 inhibition effected by the unheated inactive antiserum (No. 11) was uncertain 

 and exceedingly slight. It is, indeed, possible that the occasional delay in 

 the appearance of the full precipitate may have been due to some slight non- 

 specific inhibition exerted by increased serum concentration. 



When, however, the inactive antiserum (No. 11) was heated to 75° C. for 

 30 minutes, it developed a pronounced inhibitory capacity — so much so that 



* Welsh and Chapman, ' Eoy. Soc. Proc.,' B, vol. 78, p. 309, 1906. 



t 0*1 c.c. of the inactive antiserum solution contained O'Ol gramme dried antiserum 

 (No. 11) and was, therefore, roughly equivalent to 0*1 c.c. undried antiserum. 



