REACTION OF THE HOST TO INFECTION 



209 



of these substances is unknown. They accompany the pseudo- 



globulin fraction of the plasma in its chemical analysis, 1 but 



the union here is probably a mere physical adsorption or very 



unstable chemical combination. Ehrlich explains the formation 



of antitoxin on the basis of his side-chain theory as follows. 



The molecule of toxin attacks 



the body cell at one of its 



side-chains or receptors which 



is best adapted to this reac- 



tion. In the resulting intra- 



molecular rearrangement the 



toxin reveals itself as a dis- 



turbing element, causing de- 



struction of that portion of 



the cell to which it has be- 



come attached. In recover- 



ing from this disturbance the 



cell overcompensates by 



forming an excessive number 



Of the particular kind of side- 



r 



chain destroyed, and some can Medical Association, 1905, p. 955.) a, 



of the excess side-chains are 



detached, and circulate in the 



. 



blood, ready to react with 

 toxin entirely apart from the cell which has produced them. 

 These constitute Ehrlich's receptors of the first order and their 

 sole effect upon the toxin is that of combining with it. The free 

 receptors circulating in the blood give it its antitoxic property. 



Precipitins. Other chemical products of bacterial growth 

 are attacked and rendered insoluble by products of the body 

 cells. Kraus 2 (1897) showed that animals injected with cultures 

 of bacteria produce a substance or substances, which circulates 

 in the blood and is capable of causing a precipitate when mixed 



1 Banzhaf, Johns Hopkins Hospital Bull., 1911, Vol. XXII, pp. 106-109. 



2 Wiener klin. Wochensckr., 1897, X, p. 736. 



14 



. . IG - 85.-Receptor of the first order 

 uniting with toxin. (Journal of the Amen- 



the toxm molecule; e, haptophore of the cell 

 receptor. 



