SENSITIZATION AND TOXICITY. 387 



case of egg albumin one twenty millionth of a 

 gram sufficed for sensitization (Wells), and about 

 one thousand times that amount was required for 

 a toxic dose. It was also found that by heating 

 to 90 or 100 C. it became much more difficult 

 to cause intoxication in sensitized animals than 

 to sensitize them. Besredka concluded from these 

 experiments that sensitizing and toxic substances 

 were distinct from each other. Vaughan and 

 Wheeler by digestion with hot absolute alcohol and 

 sodium hydrate obtained a separation of albumin 

 into two parts, one of which showed a marked 

 sensitizing property and but little toxicity (alcohol 

 insoluble portion) ; the other portion (alcohol 

 soluble), a more highly toxic action. They con- 

 cluded that toxic and sensitizing substances were 

 present in the same molecule and that by their 

 process a splitting of the molecule into toxic and 

 sensitizing groups was obtained. 



The work of Vaughan and Wheeler was done 

 on whole egg white and other crude proteins. 



Wells, working with pure crystallized albumin, 

 obtained toxic and sensitizing action in this way 

 in quantities smaller than those represented by 

 Vaughan's minimum sensitizing and toxic split 

 products. It seems possible, therefore, that by the 

 process of Vaughan and Wheeler amounts of pro- 

 tein too small to produce toxic effects, but capable 

 of sensitizing, escaped splitting through alcohol 

 precipitation while the alcohol soluble portion con- 

 sisted of toxic split products. The action of heat 

 may be due to the fact that both toxic and sensi- 

 tizing substances are equally influenced, but that 

 the apparent effect is greater on toxicity because 



