24 Predisposition and Immunity. 



or merely a condition of irritability or partial injury. If the 

 injury be partial tliat part of the cell [protoplasmic molecule] 

 which remains sound restores the defect. In this condition of irri- 

 tability or stimulation there is a reaction on the part of the cellular 

 protoplasm left with its vital centre intact to regenerate the 

 receptors destroyed by the toxic influence. Following a law 

 recognized by Weigert, regeneration in the cells of an organism is 

 usually productive of more of the substance than originally ex- 

 isted at the site of loss ; and so here the restoration is often so 

 active that an excessive number of receptors are supplied to 

 replace those which have been destroyed. "Such an excess of 

 receptors constitutes a useless ballast for the cells and the extra 

 ones are thrown out into the blood and circulate therein" (Ehr- 

 lich, Wechsberg). The presence of these free receptors in the 

 blood, representing haptophores or chemically combining sub- 

 stances, affords opportunity for materials which have gotten into 

 the blood and which have chemical affinity for them, having come 

 in contact, to enter into* combination with the receptors. Thus 

 held by these free receptors, such substances are prevented from 

 involving the cellular protoplasm, and as a result the cells and 

 the whole individual are protected from the disease. 



This power of molecular combination differs in the different 

 cells of the same individual and in the cells of different species 

 of individuals. One species may possess no cells containing the 

 elements essential for combining with a certain toxine; there 

 would then be absolutely no chemical affinity shown between the 

 cellular molecules and the toxic molecules, and a priori the latter 

 must be without effect. In such a case the toxine, perhaps in 

 large quantities, may remain for weeks in the blood and general 

 circulation without any harm resulting to the individual. Such 

 instances are examples of natural immunity. On the other hand, 

 an individual may possess a vast number of receptors not merely 

 in the general body, but each cell, each corpuscle, for example, 

 may contain a mass of material capable of combining with sub- 

 stances of one or other kind. In classification of these receptors 

 it is customary, following Ehrlich, to distinguish them as of 

 I, II, III, etc., orders. 



The first order (unieeptors) includes receptors having only 

 one haptophore group for poisons (toxines) and utilizing this for 

 combination with such substances ; they are called antitoxines. 

 The presence and formation of antitoxines is illustrated by the 



