1156 PHYSIOLOGY 



as in the case of the reaction of toxin and antitoxin. Thus if two 

 solutions of fuchsin be made and to each a sheet of filter be added, 

 but in one case the paper be added at once, and in the other case in three 

 parts at intervals of twelve hours, at the end of thirty-six hours the paper 

 which has been added in parts will have removed more dyestuff from 

 the solution than is the case where the whole amount of paper was 

 added at once. In the same way, when treating a suspension of 

 bacilli with an agglutinating serum, it is found that the successive 

 addition of the bacillary suspension to the serum removes more 

 agglutinin from the solution than when the addition is made at one 

 time. 



The interactions therefore between these bodies must be looked 

 upon as special examples of the group of phenomena known as adsorp- 

 tion, such as the adsorption of iodine from- solutions by charcoal, of 

 iodine from water by starch, or of ammonia by charcoal. The exact 

 adsorption which takes place must be a function of the chemical con- 

 figuration of the substance forming the surface, since otherwise it 

 would be impossible to account for the extremely specific character 

 of the interaction between toxins and their corresponding anti- 

 toxins. The interaction must therefore be assigned to that special 

 class, in which we have already placed the action of ferments, which 

 is not entirely chemical nor entirely physical, but depends for its 

 existence on a co-operation of both chemical and physical factors. 



How are we to account for the production of the antitoxin as a 

 result of the injection of toxins into the body, a production which is 

 proportional to, but far transcending in amount, the toxin injected ? 

 In all the speculations on the mode of production and action of anti- 

 toxins an important part has been played by a conception put forward 

 by Ehrlich in 1885 of the nature of the living protoplasmic molecule. 

 According to this conception, which is spoken of as the ' side-chain 

 theory,' each unit of living matter consists of a centrally placed 

 protein group with a number of side-chains attached to it, on the 

 analogy of the hypothetical configuration of the benzene ring, to each 

 corner of which may be attached an aliphatic chain. To explain the 

 phenomena of nutrition and oxidation Ehrlich regarded some of these 

 side-chains as corresponding to unoxidised food substances, while 

 others of the side-chains had a strong affinity for oxygen and might be 

 regarded, when fully saturated with this substance, as peroxide in 

 character. Activity in such a unit would be associated with inter- 

 action between these two sets of side-chains. As a result the food 

 chain would be converted to carbon dioxide and an affinity left 

 unsaturated until it could take up another food-molecule. In the same 

 way the oxygen side-chain, having lost the greater part of its oxygen, 

 would have a strong affinity for this element and would re-saturate 



