According to this ingenious conception, the formation of antitoxins is hence absolutely independent of the action of the toxophore elements on the cellular elements, and it suffices that these possess receptors or side chains capable of uniting with the haptophore groups of the toxin. This explains why it has been possible to produce antitoxins from toxins which have lost some of their toxic properties, but which have preserved their property of uniting with antitoxic substances. Ehrlich gives the name toxoids to those modified toxins that have lost their toxophore groups, while the haptophore group, the producer of the immunizing substance, is still preserved intact.
According to Metchnikoff's theory, which is very similar, it seems quite possible that the phagocytes, thanks to the facility with which they absorb poisons, occupy an important place as producers of antitoxins. It has not been possible so far to verify this theory in our at present imperfect knowledge regarding this subject. The domain of immunity has, however, made brilliant conquests during these last few years, so that we should not despair of arriving at a definite solution before long.
In the vaccinated animal the antitoxin is reproduced, and it is possible to obtain several times, from the vaccinated animals, successive portions of antitoxic serum.[50] The protective power of these antitoxins is absolutely marvelous. An animal accustomed gradually to the tetanic virus yields a serum containing an antitoxin a thousand times more active than the virus.
According to Vaillard, a quintillionth of a cubic centimeter of this antitetanic serum suffices to preserve one gramme of living mouse from the effects of a dose of tetanic serum that would otherwise be surely fatal.
In the animal, the antitoxins are eliminated mostly by the fluids of the body, and particularly by the urine. Ehrlich has demonstrated that they also pass into the milk, and this fact is confirmed by a large number of observers. It explains the immunity acquired by nurslings, and which is transmitted by the milk.
Serotherapy.—The search for antitoxins and their rôle in the etiology of infectious diseases are fundamental points in actual therapy. It has been demonstrated that the serums of certain vaccinated animals enjoy very extended antitoxic therapeutic properties; for instance, the serum of vaccinated rabbits is an antivenom towards erysipelas; and the sterilized cultures of the pneumococcus or of the Bacillus pyocyaneus prevents infection of carbuncle (anthrax).
The antivenomous serum of the ass immunized by injections of increasing doses of the venom of the terrible naja is a perfect prophylactic and curative, not only as regards the venom of this serpent, but also against that of the crotalus, trigonocephalus, and viper.
We shall take up the study of serotherapeutics in another volume of this collection.