ANAPHYLACTOGENS, OR ALLERGENS 545 



While, therefore, it is probable, although it has not been definitely 

 proved, that nothing less than the entire protein molecule is capable of 

 producing the typical reaction, the questions arise whether the whole 

 molecule, or only a certain group thereof, determines the specificity, 

 and whether the whole molecule, or only a portion, is concerned as the 

 sensitizing agent. It is now generally accepted that both the sensitizing 

 and the intoxicating agents are one and the same protein, and the older 

 view, which held that in a mixed protein substance, such as blood-serum, 

 corpuscles, egg-albumen, etc., one protein is present that sensitizes and 

 another that intoxicates, is probably erroneous. Besredka, for instance, 

 finds that when a protein used to produce intoxication is heated it is less 

 likely to prove fatal, and he concludes that proteins contain a thermosta- 

 bile sensitizing and a thermolabile intoxicating portion. Doerr and 

 Russ, however, have shown by carefully conducted experiments that 

 heat affects both properties of proteins to the same degree. Since pure 

 proteins, as, e. g., highly purified edestin, which is believed to be a chem- 

 ical unit, act as exquisite sensitizers and intoxicants, it seems reasonable 

 to believe that the sensitizing and poisonous group are constituents of 

 the same protein substance. Whether or not both sensitizing and 

 intoxicating groups are contained in each single molecule of a pure pro- 

 tein is a question that cannot be answered until we can be certain that 

 absolutely pure proteins are secured to start with, and until our methods 

 of effecting its cleavage have been perfected. Vaughan and his cowork- 

 ers have long maintained that a sensitizing non-poisonous and a non- 

 sensitizing toxic portion are groups of the same molecule, which they are 

 able to obtain in vitro from animal, bacterial, and vegetable proteins by 

 a method of splitting with sodium hydroxid in absolute alcohol, as 

 described in the chapter on Infection. The toxic intramolecular group 

 is regarded as non-specific, and the same for all proteins, which explains 

 the identity of the symptoms of anaphylactic shock whatever the pro- 

 tein by which it is induced. The non-toxic sensitizing group, however, 

 is specific, although it may not itself be a protein, or at least a biuret 

 bodj^. Whether or not all proteins contain a sensitizing group has not 

 been determined. In keeping with his theory of the role of the toxic 

 moiety of a split protein molecule in the production of disease, Vaughan 

 believes that when proteins are introduced parenterally into animals, 

 the non-toxic portion stimulates the body-cells to elaborate specific fer- 

 ments, constituting the phase of sensitization, so that when this protein 

 is subsequently introduced, digestion rapidly takes place with the 

 liberation of the toxic substance responsible for the characteristic symp- 

 35 



