THE INFLUENCE OF THE ORGANISM UPON TOXINS.—Metchnikoff (_Ann. de l’Instit. Pasteur_, November 25, 1897,) has applied the method of comparative pathology to the question of the mechanism by which the animal organism prepares antitoxins, and the laws which regulate their production. By growing bacteria and lowly fungi upon culture media containing toxines he was enabled to show that the virulence of the latter was in most cases diminished and sometimes destroyed. In any case these microbes have no influence in the production of antitoxins, and the idea of preparing them by this means must be abandoned. The animal organism alone being capable of producing antitoxins, the next point was to find out whether this was a property common to all animals, or limited to the superior. Metchnikoff found that the injection of large quantities of tetanus toxin into scorpions and the larvæ of other arthropods produced no antitoxin. The toxin remained for months in the blood or tissues without losing its properties; similar results were obtained when it was taken into the alimentary canal of the leech. It was hence shown that even those invertebrates in which antimicrobic phagocytosis is most marked are utterly incapable of producing antitoxins. Coming next to vertebrates, no power of producing antitoxin is possessed by fish or amphibia; it first appears in reptiles, but not in all kinds. Thus tortoises, like invertebrates, can retain tetanus toxin in the blood for a lengthened period without forming antitoxins; it is in reptiles that the production of the latter is first observed, but in them only when they are kept at a temperature higher than 30° C. If the temperature is 20° C. the results are just the same as in tortoises and invertebrates. The establishment of the antitoxic property in these cold-blooded animals is not attended with any rise of temperature, and the same is true in warm-blooded animals such as fowls. With regard to the last-named animals, whose power of producing tetanus antitoxin was first demonstrated by Vaillard, Metchnikoff has some new and important observations. He finds that practically all the toxin injected into the peritoneum passes into and remains in the blood, none of the organs being toxic after their blood has been washed out. To this an exception is found in the case of the genital organs, ovaries, and testicles, which possess the power of fixing some of the circulating toxin. This they share with the leucocytes, to the toxicity of which that of the blood is due. After a while the toxic power of the blood diminishes, and after passing through a neutral period it becomes antitoxic. It is now found that with the exception of the generative organs, none of the organs when freed from blood possess any antitoxic power. The genital glands are found to be markedly antitoxic, but the author brings evidence to show that the antitoxin is not manufactured by them, but is absorbed from the blood, so that in the fowl the antitoxic