The modern employment of serums in the treatment of zymotic diseases goes a long way towards explaining the fact of the immunity of individuals in respect to bacterial poisons. But the possibility of immunity against such poisons as arsenic, opium, or serpent venom appears to rest on a different basis. In 1896 Professor (now Sir) Thomas R. Fraser, M.D., F.R.S., reported to the Royal Institution a long investigation dealing with the alleged resistant power of certain tribes or sects in India, Africa, &c., who can suffer the bites of unquestionably venomous snakes without becoming seriously affected. After quoting numerous reports from old and recent works showing that this immunity is an actual fact, Professor Fraser described a long series of experiments extending over many years with venom which he had obtained from India, America, Africa, and Australia. The venom, he stated, is a complex substance and is not a ferment. Ascertaining the minimum lethal dose for each animal he experimented on frogs, cats, rabbits, guinea pigs, and other animals, and beginning with one-tenth, one-fifth, or one-half of that dose, and gradually increasing it, he found it possible to administer four or five times, and in the case of rabbits up to even fifty times the lethal dose. From the immunised animal a serum was prepared which was antidotal in very minute quantities if mixed with the venom, but if administered separately by hypodermic injection, though at the same moment with the venom, some twelve and a half times as much was found to be necessary, and it was estimated for a normal bite of an average man no less than 11½ ounces would have to be administered hypodermically soon after the bite to prevent probably a fatal result. The most interesting observation was that the poison taken into the stomach was almost innocuous, and yet exercised a protective effect. In many of the narratives given by travellers describing the feats of the snake charmers it has been related that they will squeeze the venom from the serpent’s mouth and swallow it. This would evidently be one of their methods of rendering themselves proof against the poison when injected by a bite. Professor Fraser’s paper is published in full in “Nature” April 16 and 23, 1896. The author gives his reasons for believing that the action of the antidote is chemical. MODERN TOXICOLOGY.