66 GENERAL AND PHYSICO-CHEMICAL. 



In consideration of what has been said (page 58) about enzymotic 

 syntheses it seems very possible in the retardation of enzymotic cleavages 

 by means of cleavage products that we are dealing with synthetic 

 processes where the cleavage products supply the material. This is espe- 

 cially shown by the above-mentioned investigations of ROSENTHALER 

 on emulsin that the retarding action of benzaldehyde or of hydrocyanic 

 acid upon emulsin action, as shown by TAMMANN/ is explainable by 

 syntheses. LicnwiTZ 2 considers the interaction of the products as a 

 reversible paralyzation of the enzyme. 



Appendix : Antigens and Anti-bodies. In connection with the retar- 

 dation of enzyme action we can also call attention to other similar proc- 

 esses. Under the name antigen we include those substances which, 

 when injected into animals, cause the formation of bodies in the organ- 

 ism with which they can in some way or another react. The process 

 is called immunization and the bodies formed are called anti-bodies or 

 in certain cases immune bodies. Generally these anti-bodies are specific 

 in the sense that they only react with the corresponding antigen. The 

 chemical constitution of the antigen as well as of the anti-body is not 

 known; they belong perhaps to the colloids, or at least they occur asso- 

 ciated with colloids. 



The antigens are either substances soluble in water or occur as 

 constituents of the cells. We will first discuss the antigens soluble in 

 water. 



To this group belong, in the first place, certain poisonous substances 

 of animal or plant origin (toxins), for example, snake poisons, bacterial 

 poisons, ricin (from the seeds of Ricinus communis), also enzymes as well 

 as certain proteins without special action. The reaction with the anti- 

 bodies (which are obtained in the blood serum of animals) manifests 

 itself with the poisons by the suppression of the poisonous action, with 

 the enzymes by retardation of the enzyme action, and with certain pro- 

 teins by formation of a precipitate which contains the antigen as well 

 as the anti-body. Anti-bodies of this last type are called precipitins. 



The longest known (due to the epoch-making investigations of v. 

 BEHRiNG 3 ) and best studied are those anti-bodies which are produced 

 by toxins and which neutralize the action of the toxins upon the animal 

 organism (antitoxins). According to the older view this takes place 

 by some sort of an action of the anti-body upon the cells sensitive to the 

 toxins. After it was shown that the toxins could also be neutralized 

 in vitro by the anti-bodies, it is now generally accepted that the neu- 



1 Ibid., 16, 271 (1892). 

 *Ibid., 78, 128 (1912). 

 'Deutsch. med. Wochenschr., 1892; Zeitschr. f. Hygiene, 12 (1892). 



