220 PROTEIN POISONS 



this amount and not kill. Whether the second dose kills 

 or not depends not only upon the amount of poison it 

 contains but upon the rapidity with which the poison is 

 set free. 



There has been some difference of statement concerning 

 the effect of heat on the sensitizing properties of blood 

 serum. Rosenau and Anderson 1 found that animals could 

 not be sensitized with serum which had been heated at 100. 

 Doerr and Russ 2 placed the point at which loss of sensitizing 

 properties occurs at 80. Kraus and Volk 3 raised it to 90. 

 Besredka has straightened out this matter and has correctly 

 shown that the sensitizing properties of a protein are in part 

 at least dependent upon its physical state, and that diluted 

 serum may be heated even to 120 without losing its 

 capability of sensitizing. It is probable that no protein 

 completely sensitizes the body cells unless it be in at least 

 partial solution. Heating undiluted blood coagulates the 

 protein, and in this way leads to a decrease of its stimu- 

 lating effects upon the body cells. Besredka has shown that 

 the sensitizing property of blood serum is thermostabile. 

 Wells 4 has very properly pointed out that it is the physical 

 change induced in the protein by coagulation and not 

 chemical alteration, which decreases its efficiency as a 

 sensitizer, and he calls attention to the fact first shown 

 by Besredka that proteins not coagulated by heat, do not 

 decrease in their sensitizing effects when their solutions are 

 boiled. This is true of casein, for instance, but when milk 

 sours and coagulation of the casein results it is not so ready 

 a sensitizer. Wells, furthermore, shows that other methods 

 of coagulation, as by precipitation with alcohol, lessen the 

 sensitizing properties. He suggests that the finely coagu- 

 lated particles of protein may be seized upon by phagocytes 

 and destroyed. In confirmation of this we have found that 

 proteins insoluble in water, such as edestin, sensitize more 

 efficiently when dissolved in salt solution than when sus- 



1 Hygienic Laboratory, Bulletin No. 45. 



2 Zeitsch. f. Immunitatsforschung, i, 110. 



3 Ibid., 731. " Jour. Infect. Dis., v. 



