70 PHYSICAL CHEMISTRY IN BIOLOGY. 



called anti-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 associated with 

 colloids. 



To the antigens 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. 



If certain cells, for example, bacteria, blood-corpuscles, and sperma- 

 tozoa are injected into animals, then anti-bodies are formed which have 

 been called immune- bodies (also amboceptors or sensibilizators) . By them- 

 selves the immune bodies are inactive, but form with complements, sub- 

 stances occurring in normal serum, so-called cytotoxins, which destroy 

 the kind of cells active in their formation. These cytotoxins are called 

 bacteriolysins, hcemolysins, etc., according to the kind of cells used. 

 The immune bodies are specific and also stable against heat; the com- 

 plements can act together with different immune bodies and are very 

 unstable, as they are generally destroyed by heating to 56 C. for 

 one-half hour. Other anti-bodies, produced under the influence of 

 injected cells, show their action by flocking together and agglutinating 

 the cells set free in their formation. These anti-bodies are called agglu- 

 tinins. 



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

 BEHRING l ) 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- 

 tralization is brought about by some sort of a combination between the 

 toxin and 'the anti-body. The views are very contradictory in regard 

 to the nature of this combination and the manner in which it is formed. 



The oldest theory, which has contributed much to our knowledge 

 of these conditions, is that of P. EHRLICH, whom we must thank for the 

 method for measuring the quantity of toxin by injection into an ani- 



1 Deutsch. med. Wochenschr., 1892; Zeitschr. f. Hygiene, 12, 1892. 



