[35] DECROLY et ROUSSE: _Arch. Int. de Pharmacodyn._, III and VI; Masoin: _Arch. Intern. de Pharmacodyn._, II, 1903. This is not, however, the case with cold-blooded animals, which, generally, are not affected by injections of poisonous toxins. Thus Metchnikoff[36] and his pupils have been able to show that the toxins introduced into certain cold-blooded animals (Oryetes nasicorius) may remain for several months without alteration in their circulation. [36] METCHNIKOFF: _L'Immunité_, Paris, 1902; MORGENROTH: Zur Kenntniss des Tetanus des Frosches. _Deutsche Med. Woch._, No. 35, 1898. If we consider the facts of the theory of Ehrlich's lateral chains, which we have mentioned, we are led to well-defined conclusions regarding the mode of action of the toxins. In fact, since these toxins exhibit a pronounced chemical affinity for the tissues, and while, on the other hand, they can attach themselves only because of the presence of certain functional groups of the protoplasmic molecules, this union can take place only in certain specific centers. This has been fully confirmed by experiments _in vitro_. It is known, since the researches of Ehrlich,[37] Wassermann and Takaki,[38] Marie,[39] Metchnikoff,[40] and a host of other scientists, that this fixation is due to a clearly elective property. It is for this reason that the tetanus toxin fixes itself only upon the nervous tissue, and that in this action all passes as if the nervous tissue had been provided with functional groups possessing an elective affinity for the tetanic poison. [37] EHRLICH: _Berl. Klin. Woch._, No. 12, 1898. [38] WASSERMANN and TAKAKI: _Berl. Klin. Woch._, _Med._, p. 5, 1898. [39] MARIE: Sur les Propriétés Antitoxiques aux Centres Nerveux de l'Animal Sain. _Ann. Inst. Past._, 1898, p. 1. [40] METCHNIKOFF: Recherches sur l'Influence de l'Organism sur les Toxines. _Ann. Inst. Past._, 1899, p. 82. =Means of Defense Possessed by the Organism against the Action of Toxins.=--We have already seen that the renal organs serve for the elimination of the toxins normally produced in the organism by the simple play of its cellular mechanism. Experience has shown that the toxins introduced from without into the circulation are generally finally eliminated, even though in the meantime the modifications they have imprinted on the economy may be transmitted hereditarily; and that their influence on the general nutrition and the normal functionation of the entire organism persists even after their elimination. Much has been said regarding the elimination of these toxins by the urine, but the experiments made by Métin, at the Institut Pasteur, have shown the inaccuracy of this assumption, and it has been necessary to seek another.