128 Immunity 



agglutinins, one of which acts upon the bacteria directly, the 

 other through the flagella. The occurrence of these two 

 bodies explains some of the incompatible results of previous 

 experiments. 



The reaction of agglutination has been applied with more 

 or less success for the differentiation of all kinds of closely 

 related bacteria, and in cases where the cultural and mor- 

 phologic resemblances of closely related species are great, 

 as in the case of the typhoid and para-typhoid bacilli (q.v.), 

 has been found a valuable adjunct to the laboratory methods. 

 It is also employed with great success in the diagnosis of 

 typhoid and paratyphoid fever, various forms of dysentery, 

 and with varying success in many other diseases. 



The agglutinins when injected into animals effect definite 

 chemico-physiological reactions with the formation of anti- 

 bodies inhibiting their own activity. 



III. The Antitoxins. In the synopsis of immunity ex- 

 periments already given the history of the discovery and 

 development of the anti-bodies has been outlined, together 

 with references to the original contributions in which they 

 were made public. In the second part of this work the 

 chapters dealing with the individual infectious diseases will 

 contain additional information upon the mode of prepara- 

 tion, therapeutic action, etc., of the antitoxins in particular. 

 At this point, however, it seems well to gather together a 

 few general facts regarding the anti-bodies, without which 

 many of their important practical bearings might be mis- 

 understood. 



In the section upon the "Explanation of Immunity" we 

 have seen that the best mode of accounting for the occur- 

 rence of antitoxins is afforded by Ehrlich in the lateral-chain 

 theory. He regards them as cell haptophores receptors 

 that are found in excess of the requirements, by cells fre- 

 quently stimulated by the presence of bacteria-products 

 possessing adapted haptophores. The receptors are under 

 normal conditions engaged in maintaining the proper nutri- 

 tion of the cell; under abnormal conditions (as when pre- 

 empted by the inert or injurious haptophores of the bacterio- 

 products) are obliged to increase in number to compensate 

 for the damage done the cell. The substances by which 

 anti-body formation can be stimulated must bear a resem- 

 blance to the normal nutrient substances absorbed by the 

 cells in that they are provided with haptophore groups 

 corresponding with the haptophore groups of the cells and 



