Page:George Archdall Reid 1896 The present evolution of man.djvu/230

218 unchanged in the blood and tissues. Pasteur's memorable experiments on rabies were held to confirm this view. It was thought that his thoroughly desiccated cords contained the waste products, but not the living organisms of hydrophobia, and that the rationale of his treatment of that disease lay in disproportionately increasing the waste products' as compared to the microbes in the blood and tissues of the infected person.

There is perhaps a modicum of truth in this theory, for the blood serum of animals which have acquired immunity through illness against certain diseases—e.g. cholera, erysipelas, anthrax, diphtheria, &c. —has greater bactericidal power than the serum of animals yet susceptible; but that the waste product theory is utterly insufficient to account wholly for acquired immunity is decisively proved by the fact that the micro-organisms of certain diseases are able to flourish in the serum withdrawn from immune animals, which should of course contain the waste products if they exist in them. The anthrax bacillus is a case in point, and it has been found, moreover, that this micro-organism will live and grow in the anterior chamber (in which there are normally no phagocytes) of the eye of an immune animal, where also the waste products if present in the animal should likewise be present. A different interpretation of Pasteur's experiments must therefore be sought.

Pasteur furnished the key to the problem by some other experiments. He found that the virus of rabies is of constant strength in dogs.

"And inoculations made from dog to dog kill the animal with the same incubation period, the same