ANAPHYLAXIS 371 



stance, the quantity injected, and the interval between administra- 

 tions. To a great extent, too, the violence of the reaction is depend- 

 ,ent upon the path by which the particular substance enters the body. 



Each of these factors, therefore, requires detailed consideration 

 before we can intelligently proceed with a further analysis of the 

 condition. 



The substances with which animals may be sensitized are, in all 

 particulars, identical with the class of substances which we have char- 

 acterized as "antigens." In fact, up to the present time, there has 

 not been a single authenticated exception to this, and from our pres- 

 ent understanding of the mechanism of anaphylaxis we may safely 

 predict that no such exceptions will be found. It is the large class of 

 proteins, therefore, whatever their source, which may act as the "ana- 

 phy lactic antigens." However, in this connection as well as in the 

 larger problem of the nature of antigens in general, it has been diffi- 

 cult to decide whether or not the antigenic property is entirely con- 

 fined to proteins or whether other substances, such as the lipoids, 

 must be included in the definition. The problem has been the same 

 here as in other serum phenomena, but much special experimenta- 

 tion has been done upon the question with particular reference to 

 anaphylaxis and the possibility of sensitizing animals with lipoids. 



As in the case of similar investigations in regard to antibody for- 

 mation, the results obtained in this work have been somewhat confus- 

 ing. Pick and Yamanouchi 34 extracted beef and horse sera with alco- 

 hol, and evaporated and redissolved the solutions until neither con- 

 tained coagulable protein nor gave the Biuret reaction. With this ma- 

 terial they obtained a few positive anaphylactic experiments. Simi- 

 larly curious are the results of Bogomolez, 35 who succeeded in sensi- 

 tizing and producing shock with the lipoids extracted from egg yolks. 

 Although such experiments would tend to persuade us that lipoidal 

 substances may actually have sensitizing, and therefore antigenic, 

 functions, this does not follow necessarily. As Pick and Yamanouchi 

 themselves point out, it is practically impossible to demonstrate with 

 certainty the presence of slight traces of proteins as impurities in li- 

 poid preparations, and we know especially from Rosenau and Ander- 

 son's work how minute are the quantities of antigen which still serve 

 to sensitize. It is possible, moreover (a thought developed particu- 

 larly by Pick and Schwartz 36 and by Landsteiner 37 ), that we are 

 dealing in many cases with combinations of protein and lipoid a 

 form of chemical substance of which very little is known analytically, 

 but the existence of which many biological facts lead us to assume. 



That^h&cmaphAilacMr, reaction is specific we have mentioned in 



34 Pick and Yamanouchi. Zeitschr. f. Immunitatsforschung, Vol. 1, 1909. 



35 Bogomolez. Zeitschr. f. Immunitatsforschung, Vols. 5 and 6, 1910. 



36 Pick and Schwartz. Biochem. Zeitsch., 15, 1909. 



37 Landsteiner. Referat. "Weichhardt's Jahresbericht," 6, 1910. 



