Effect of Heat on Preclpitdble Sitbstance 117 



The effect of Heat upon the Precipitable Substance. 



Linossier and Lemoine (21, iii. 1902) state that a serum dilution 

 containing so little albumin that it will not coagulate on boiling, has to 

 be boiled several minutes to destroy its precipitable substance. 



The few observations noted in the preceding table made it appear 

 that the precipitable substances in normal serum possess about the 

 same resisting power as the precipitins. The results with milk are in 

 flat contradiction, and probably due to error on the one or the other 

 side (see under Lactosera). Whereas some observers exposed undiluted 

 serum, others exposed diluted serum to the different temperatures, con- 

 sequently the results cannot be compared. 



The following experiments were carried out at my suggestion by 

 Dr Graham-Smith (29, vii. '03, p. 355). 



" The heating of specimens of undiluted ox serum (1 c.c. for 3 

 minutes), was carried out in the same manner as described for antisera. 

 Subsequently 1 : 21 dilutions in salt solution were made, and tested 

 with anti-ox serum. 



No visible change in the serum was noticed till a temperature of 

 56" C. was reached, when the serum became slightly opalescent. This 

 opalescence increased between 63 — 67° C, and was still further marked 

 at 68° C. All these specimens gave slightly cloudy solutions. At 70° C. 

 the serum became very opaque, and at 75° C. white and solid. 



