Page:George Archdall Reid 1896 The present evolution of man.djvu/243

Rh means by which higher organisms are brought into harmony with an exceedingly complex environment; but it is highly incredible that phagocytes or any other cells, when acted on by this or that toxin, should suddenly develop the power of producing this or that anti-toxin, a complex chemical substance which exactly antagonizes another highly complex chemical substance, the particular toxin presented, but no other. It would be as reasonable to attribute the resistance offered by trained skin-cells to heat to the production of an anti-pyretic substance, or the resistance offered by other kinds of trained cells to the action of nicotine, alcohol, opium, arsenic, &c., to the production of specific anti-toxic substances.

When therefore the toxins (freed from the microorganisms) of diphtheria are injected into the horse, it is highly improbable that there is elaborated in that animal an anti- toxic substance which exactly antagonizes the poison, and which, dissolved in his blood-serum, when injected into man, for that reason renders the latter resistant to the disease. On the contrary, it. is probable, since the injection of immunized blood-serum apparently does tend to produce increased powers of resistance in man, that the toxins are altered in the horse, perhaps by intracellular digestion, as suggested by Dr. Hunt; are rendered less virulent, are so altered that the phagocytes of the man are able to react to them, and thus to attain a position of advantage, whence they are able to react to the unaltered virus, to accomplish by successive efforts that which they are unable to accomplish at a single effort. It is very improbable that the animal body is a sort of "magic bottle" which produces particular anti-toxins at need, but very probable, judging by analogy, that its cells are able to vary gradually so as to adapt themselves to that change in