THE CHEMICAL MECHANISMS OF DEFENCE 1033 



course of events would be similar to that observed by Ehrlich. At no time 

 would there be complete neutralisation, owing to the fact that hydrolysis 

 constantly occurs, so that when equivalent quantities of each substance had 

 been added, the fluid would still contain a certain amount of free base 

 alongside of free acid, in addition to the salt produced by the combination 

 of the two. It is impossible, however, to account for all the phenomena 

 presented in the neutralisation of toxin by antitoxin in this simple manner. 

 Thus seventeen parts of ammonia would neutralise exactly an equivalent 

 quantity of boracic acid, whether these substances were dissolved in 10 c.c. 

 or in 100 c.c. of water. If, however, it be found that 1 c.c. of antilysin 

 exactly neutralises 1 c.c. of lysin, these two substances will no longer be in 

 equilibrium when the whole is diluted up to 10 c.c. with water. If a neutral 

 mixture of lysin and antilysin be taken and filtered under pressure through 

 a gelatin filter, no lysin or antilysin passes through the filter, so that the 

 residue on the filter becomes concentrated. On examining this residue it is 

 found that it has a strong hsemolytic action, and the same is true of the 

 substance which may be obtained by melting the gelatin out of the pores of 

 the filter. It is evident that, even in a neutralised mixture, both free lysin 

 and free antilysin, or free toxin and free antitoxin, are present, and it needs 

 only the alteration of the physical condition of the mixture in order to 

 display the action of one or other of these bodies. How then are we to 

 regard this combination of toxin with antitoxin ? Craw has pointed out 

 that the combination is in all respects comparable to that which occurs 

 between absorbing surfaces and many dyestuffs. If we place some filter 

 paper in a solution of fuchsin or Congo red, the filter paper will take up the 

 dye substance. The amount taken up by the paper will increase with 

 increase in concentration of the solution. There will, however, be a ten- 

 dency to the formation of false equilibrium points, 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 adsorption, 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 configuration 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 

 antitoxins. The interaction must therefore be assigned to that special 

 class, in which we have already placed the action of ferments, which is not 



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