100 NATURE OF UNION OF TOXINS AND TISSUES 



however, need not, and in all probability do not, unite with the 

 protoplasm in this way. Ehrlich, basing his theories on the fact that 

 certain alkaloids and other substances can be extracted from their 

 combinations with organic matter by simple means, has suggested 

 that the union of non-proteid poisons with protoplasm is less firm 

 than in the other case. This seems doubtful, for nothing could 

 be much firmer than the combination of nitrate of silver or similar 

 bodies with the tissues. And we know as a matter of fact that 

 the toxin-protoplasm compound is not necessarily a stable one. 

 Emulsions of tissues will abstract tetanus toxin, and retain it on 

 washing, but give it up again in a free state when allowed to stand 

 for some time in contact with normal saline solution. However 

 this may be and the point is not of importance we may readily 

 admit with Ehrlich that it is highly probable that proteids unite 

 with protoplasm in a manner fundamentally different from alka- 

 loids, etc. The former process follows on physiological lines, 

 whilst the latter is a pathological process entirely, and one which 

 has no counterpart in normal nutrition. The former may be 

 compared to the insertion of the key in the lock, the latter to the 

 violent smashing of the lock. If this is the case, it is easy to 

 see that " chemical " poisons cannot be expected to give rise to 

 the production of antibodies. It is true that if a cell is already 

 secreting antibodies, we might expect that a substance which 

 stimulates the general metabolism of the cell and increases the 

 rapidity of the vital processes might temporarily increase this 

 production, and we have seen that this is the case with pilo- 

 carpin, which stimulates the production of diphtheria antitoxin in 

 an immunized horse. This is an entirely different process, and 

 one that is easily explicable on the side-chain theory. 



It is necessary, therefore, to determine whether all the sub- 

 stances which give rise to the production of antibodies on injec- 

 tion are proteids. We must admit at the outset that in many cases 

 this cannot be proved ; the chemical constitution of toxins, enzymes, 

 and many other antigens is as yet quite unknown. But in the 

 cases in which the chemical composition of the primary substance 

 is ascertained we find it to be invariably of proteid nature ; thus, 

 solutions of any of the coagulable proteids will give rise to the 

 production of precipitins ; the proteid substances present in the 

 body of bacteria give rise to the production of agglutinins, which 

 are themselves of a proteid nature, and will, on injection into 

 suitable animals, give rise to anti-agglutinins ; the proteid con- 



