AGGLUTINATION AND DISSOLUTION. 175 



normal rabbit serum, is rapidly hemolyzed. But, with the same 

 amount of defibrinated blood and normal serum, the addition of 

 relatively small doses of active serum heated either to 60 degrees or 

 to 70 degrees shows that dissolution takes place more slowly with 

 the serum heated to 70 degrees ; that is, the sensitizing property of 

 the serum has been diminished by heating to 70 degrees. It is very 

 attenuated, but is not completely destroyed by heating for half 

 an hour to 75 degrees. 



It may be noted that a mixture of defibrinated hen blood, normal 

 serum, and active serum heated to 70 degrees is hemolyzed with- 

 out any preliminary agglutination; the corpuscles are soon reduced 

 to separate nuclei. If the agglutinin is not destroyed it has at 

 least become too feeble or too small in amount to produce clump- 

 ing; sensitization, however, still goes on. 



Precipitating property. — In addition to the antihematic property 

 in active rabbit serum we should note its property of forming a 

 precipitate with normal hen serum. We have already considered 

 this question in a preceding article* and in this connection we 

 have mentioned the researches of Tchistovitch, to whom we owe 

 the first observations of a similar phenomenon. When the two 

 sera are mixed a turbidity appears that at first is slight but soon 

 increases and finally condenses into flecks. The most abundant 

 precipitate is formed by a mixture of one or two parts of hen serum 

 with eight or nine parts of active serum. 



If, instead of treating rabbits with hen blood, hens are treated 

 with rabbit blood, their serum is found to precipitate normal rabbit 

 serum. The phenomenon of precipitation, however, does not occur 

 regularly in all instances examined ; the serum of guinea-pigs treated 

 with rabbit blood, for example, causes no precipitate with rabbit 

 serum. A mixture of sera from normal animals of different species 

 never causes a precipitate. 



B. Antitoxic property. — It seemed probable that we should be 

 able to produce sera endowed with an antitoxic property and 

 capable of opposing the destructive action of certain given sera on 



* See p. 142. We shall not here consider the significance of this phenomenon. 

 We have already mentioned the effect of heat on the precipitating property and 

 determined to what extent the precipitins are specific. We may recall that the 

 serum in question (serum rabbit > hen) also precipitates pigeon serum. 



