2l6 GENERAL BIOLOGY OF MICRO-ORGANISMS 



) 



union here is probably a mere physical adsorption or very un- 

 stable 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 reaction. In the re- 

 sulting intra-molecular re- 

 arrangement the toxin reveals 

 itself as a disturbing element, 

 causing destruction of tljat 

 portion of the cell to which 

 it has become attached. In 

 recovering from this disturb- 

 ance the cell overcompen- 

 sates by forming an excessive 

 number of the particular kind 

 of side-chain destroyed, and 

 some of the excess side- 

 chains are detached, and cir- 

 culate in the blood, ready to 

 react with toxin entirely apart 

 from the cell which has pro- 

 duced them. These consti- 

 tute 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^ (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 

 with the clear filtrate of the cultures of the same bacteria. The 

 parenteral introduction of any foreign protein in solution stimu- 

 ' Wiener klin. Wochenschr., 1897, X, p. 736. 



Fig. 87. — Receptor of the first order 

 uniting with toxin. (Journal of the Ameri- 

 can Medical Association, ipoSt p. 9SS-) o. 

 Cell receptor; 6, toxin molecule; c, hapto- 

 phore of the toxin molecule; d, toxophore of 

 the toxin molecule; e, haptophore of the cell 

 receptor. 



