l6o METHOD OF COMPLEMENT FIXATION 



If such, an organism is injected with tetanospasmin the latter toxin is 

 bound by the free receptors in the serum, and thus the respective " sessile" 

 receptors attached to the cells are prevented from coming in contact with 

 the poison. Inasmuch as the free receptors possess no functional radicle 

 which can be injured, the toxin remains entirely innocuous for the indi- 

 vidual. Such protective bodies lend to the organism its attained immunity 

 and are known as antitoxins. Their function can be compared to lightning 

 rods. 



v. Behring well expresses their action when he states that the same 

 elements, which attached to the cells render the body susceptible to toxic 

 substances, when circulating freely in the blood serve to protect it. 



The antibodies against toxins and ferments are of the simplest form. 

 They possess only a binding group which has an affinity toward the hapto- 

 phore group of the toxins and ferments. They, therefore, belong to the 

 class designated by Ehrlich as "haptines" of the first order. 



To the haptines of the second order belong the agglutinins and pre- 

 cipitins. They possess besides a haptophore group also an agglutinophore 

 or precipitinophore group by virtue of which agglutination or precipitation 

 takes place. 



Belonging to the haptines of the third order are the class of amboceptors 

 which have in addition to the haptophore group also a complementophile 

 group for their union with the complement. 



These hypotheses of Ehrlich greatly simplify the explanation 

 Citron's of many serum reactions as well as many of the phenomena 

 Tuberculin associated with the action of tuberculin. In all probability 

 Theory, the healthy cells which exist in the tuberculous focus and 

 which are capable of reaction, produce the antituberculin. 

 Christian and Rosenblatt offered experimental evidences for this state- 

 ment. They demonstrated that tuberculous guinea-pigs, in whom anti- 

 tuberculin was produced by tuberculin injections, showed a diminution 

 of antituberculin in the blood when tuberculous glands were removed by 

 operation. 



The antituberculin production by the cells is a transitory action arising 

 only when tuberculin has spontaneously or artificially reached the circu- 

 lation. Following this stage of activity there comes a period of quiescence 

 during which no free antituberculin can be found in the serum. The cells, 

 however, are supplied with a great many more sessile receptors than usually: 

 they possess a higher affinity toward tuberculin and produce antituberculin 

 much more readily than normal cells. 



This also explains why the smallest amounts of tuberculin produce a 

 reaction in tuberculous and not in the normal individuals. In the former, 

 the cells in the zone surrounding the tuberculous focus are abundantly 

 supplied with receptors, so that on the injection of tuberculin, its action 



