472 Phenomena exhibited by Precipitin Antisera. 



exists between the capacity for solution and the capacity for inhibition 

 of precipitate, but we have still more striking evidence to offer. For 

 example, an antiserum rendered inactive, but non-inhibitory, by heating to 

 72° C, has no power of dissolving precipitate, but when the antiserum is 

 rendered inhibitory, by heating to 75° C, it coincidently acquires the power 

 of solution. Antiserum (No. 11), rendered inactive, but non-inhibitory, by 

 long-continued desiccation, did not dissolve precipitate, but when heated 

 to 75° C, and thereby made capable of inhibiting, it also became capable 

 of dissolving precipitate. When antisera are mixed with a sufficiency of 

 homologous protein, their precipitable content may be entirely thrown out 

 of solution and the antisera rendered inactive. Such inactivated antisera, 

 when heated, do not gain the power of preventing precipitation (a corre- 

 sponding result was obtained by Miiller in respect of lactosera), and neither 

 do they gain the power of dissolving precipita. 



Further, an antiserum rendered inhibitory and solvent, by heating to 

 75° C, has almost completely lost both capacities after heating to 85° C. 

 for 10 minutes, and has completely lost both by exposure to 85° C. for 

 30 minutes, or to 100° C. for five minutes. Such destruction of inhibitory 

 and solvent capacity does not reactivate the antiserum, nor does the addition 

 of heated or unheated natural rabbit serum restore its inhibitory or solvent 

 capacity. 



Notwithstanding many experiments of the above nature, we found it 

 impossible to dissociate the capacity for inhibition from the capacity for 

 solution of precipitate. Both appear and disappear together, and it would 

 seem not unreasonable to draw the further conclusion that an antiserum 

 acquires the power of preventing precipitation in virtue of its acquiring the 

 power of dissolving precipita ; in other words, that an essential part of the 

 mechanism of specific inhibition is the development of a no less specific 

 capacity for solution of precipitate. 



Conclusions. 



1. Inactivation and inhibition are separable phenomena, the former 

 appearing without the latter in hen-egg antisera heated to 72° C, or exposed 

 to long-continued desiccation, the latter not becoming appreciable until the 

 antisera are heated to 75° C. 



2. Inhibition and solution of precipitate by heated antisera are specific 

 inseparable phenomena. 



3. The specific capacity for dissolving precipitate acquired by heated 

 antisera is probably an essential part of the mechanism of specific inhibition. 



