470 



Prof. D. A. Welsh and Dr. H. G. Chapman. [Apr. 30, 

 Table I. 



No. 



Homologous protein, 

 0005 c.c. 



Active antiserum, Heated antiserum, 

 0-1 c.c. O'l c.c. 



Precipitation. 



1 



2 

 3 



4 

 5 

 6 



7 



8 



9 



10 



Hen-egg white 

 Ostrich-egg white 

 Horse serum 

 Hen-egg white 

 Ostrich-egg white 



Hen -egg white 

 Horse serum 

 Ostrich-egg white 

 Hen- egg white 



Hen-egg 



Ostrich-egg 



Horse 



Ostrich-egg 



Hen-egg 



Ostrich-egg 



Hen-egg 



Horse 



Hen -egg white 



Ostrich-egg 



Hen-egg 



» 



Ostrich-egg 

 >> 



» 



>> 



Inhibited 

 Unaffected 



Inhibited 



>» 

 Unaffected 



_ >> 

 Inhibited 



»> 



The Nature of inhibition as indicated by the Specific Solubility of Precipitates 

 in Heated Homologous Antisera. 



Miiller* was the first and, so far as we are aware, the only observer 

 to point out that a precipitate resulting from a precipitin interaction was 

 soluble in the heated antiserum, but his observation had reference only to 

 lactosera. The possible significance of this phenomenon led us to under- 

 take a more extended series of tests, in order to determine how far this 

 property was possessed by other heated antisera, and how far the capacity 

 for dissolving precipitate might be identified with the capacity for 

 inhibition. 



Our experiments gave the following results : — (1) The precipitum formed 

 between hen-egg albumin and hen-egg antiserum is soluble in any hen-egg 

 antiserum heated to 75° C, but not in ostrich-egg antiserum, nor in horse 

 antiserum, similarly heated ; (2) the precipitum formed between ostrich- 

 egg albumin and ostrich-egg antiserum is soluble in ostrich-egg antiserum 

 heated to 75° C, but not in hen-egg antiserum, nor in horse antiserum, 

 similarly heated ; (3) the precipitum formed between horse serum and 

 horse antiserum is soluble in any horse antiserum heated to 75° C, but not 

 in hen-egg or ostrich-egg antiserum similarly heated ; (4) such precipita 

 are insoluble in water, in salt solution, in natural rabbit serum, and in 

 natural rabbit serum heated to 75° C, all of which are likewise non- 

 inhibitory ; (5) the amounts of heated antisera used in dissolving the 

 precipitates were the same as those used in producing inhibition (from 

 0*1 to 0*3 c.c), and where the lesser quantity was unable to inhibit, it was 

 also found to be unable to dissolve the precipitate. When a precipitate 

 was soluble in heated antiserum, it rarely happened that the whole of the 



* Miiller, loc. cit., p. 175. 



