118 



The Nature of Precipitin Reactions 



The quantity of precipitum formed remained constant up to 50° C, 

 but from 55° C. to 62° C. a marked diminution was noticed. At 63° C. 

 a further reduction occurred, and at higher temperatures the formation 

 of precipitum ceased. All solutions gave a good foam-test. 



The figures given below are the mean of two estimations in each 

 case. 



Normal undiluted ox serum heated for 3 minutes. 



These experiments, as far as they go, appear to indicate that an 

 antiserum can be exposed to a greater degree of heat than its 

 corresponding serum without injury, and that the precipitum-producing 

 property is completely destroyed in the latter at a lower temperature." 



Tlie effects of filtration of Normal Sera through " stone " filters. 



" It has been already indicated that the substance of " stone " filters 

 when allowed to act on serum exerts some influence on the serum 

 exposed to it. In order to further test this point ox serum was filtered 

 through a new Berkefeld filter, and through a new clean Chamberland 

 filter. After a certain quantity of serum had filtered through it was 

 removed, and specimens from it diluted and tested. It was found that 

 in the former case the precipitum-formiug power was at first diminished, 



