My views regarding the manner in which diastases act I have developed at length in my work Nature des Diastases. The close analogy between these substances and the toxins, an analogy upon which, moreover, I have dwelt at some length, permits me to refer the reader who is desirous of fuller details to the small work just mentioned.
The mode of action of diastases resembles singularly closely that of the catalytic substances, and we will admit, for the moment, that they act by intermediary combination, resulting in their rapid decomposition.
We owe to Ehrlich[31] a new conception relative to the nature and mode of action of the diastases, and which to-day plays an important rôle in all our conceptions regarding immunity.[32]
According to this scientist, the complex molecule of albuminoid substances is constituted by a fixed central nucleus, and by a number of lateral chains or receptors, fixed to this nucleus, which possess diverse accessory functions, and which serve, particularly, for the nutrition of the cells. These receptors have a great affinity for the various substances necessary for the support of the living elements, and they seize upon the alimentary substances, in normal life, just as a leaf of the Dionæa seizes a fly which serves as its food.
In these special conditions the receptors may attach themselves to the complex molecules of albuminoid substances, such as the different toxins.
Ehrlich supposes, as we have already seen, that a toxin contains two special groups—a toxophore group, which poisons, and a haptophore group, which combines with the receptor. According to this theory, the toxophore group of a toxin can act on an organism only when the haptophore group of the toxin encounters a suitable attachment or receptor.
The receptors attached to the living protoplasmic molecule attract the toxin, just as a lightning-rod attracts the lightning.
It is hence clearly proved that the toxigenic poisons exert their noxious action on the cellular elements of sensitive organisms, by entering into combination with these.
Experience has shown that they attach themselves, in a most rigorously elective manner, to the tissues, and rapidly disappear from the general circulation. Numerous facts, clearly established, attest the reality of this fixation or attachment.
It is thus that von Behring and Wernicke[33] sought to ascertain the quantity of antitoxin (we will see farther on that this name is given to those substances which neutralize the activity of toxins under certain conditions) which, introduced a certain time after the introduction of the poison, will save the life of the animal. They have experimented with diphtheria toxin, which we will study later, and they have demonstrated that, if the antitoxic serum be introduced immediately after the toxin, a dose of antitoxin twice as large as that of the toxin suffices to effect a cure.