Curare is a poison which the natives on the banks of the Amazon prepare from a bind-weed of the strychnia family. They boil the plant with several ingredients, finally obtaining a sort of blackish resin, or gummy juice, which they place in little gourds, which can be procured also in Europe. This juice is used by South American Indians for their arrows, and physiologists use it to ensure the immobility of the animal on which they are experimenting. Curare dissolves in water, and a solution of a few centigrams injected under the skin of a dog, a cat, a rabbit, will bring about the death of the animal in a few minutes. But death is not due to the arrest of the heart's action, it is due entirely to paralysis of the respiration. Therefore the curarised animal can continue to live for several hours if _artificial_ breathing be substituted for the natural breathing which is paralysed. For several hours the animal is completely motionless; the heart beats with force and regularity, provided that the insufflation of air into the lungs introduces into the blood the quantity of oxygen necessary for the life of the tissues. Now, under these conditions, as Claude Bernard has so well demonstrated, we have no proof that sensibility is abolished also. There is immobility; there is no true anæsthesia. Take two animals, one chloroformed, the other curarised; both are equally inert; but the chloroformed animal is insensible, whilst the curarised animal retains sensibility. It is impossible, therefore, to say that curare replaces anæsthetics, because _curare is not an anæsthetic_.[6] Now, in 1894 I was able to discover a substance which has all the anæsthetic properties of chloroform, and which nevertheless does not abolish reflex actions, so that physiologists are able to use it for experiments which, formerly, necessitated the use of curare. This substance is called _chloralose_; it is obtained by mixing anhydrous chloral with glucose. It is not necessary for me to describe here in detail its chemical or physiological properties; I will only say that in very small doses (about twenty-five centigrams) it is an excellent hypnotic for man, and that in larger doses, injected into the vein of a dog or a rabbit, it brings about complete anæsthesia without affecting either the breathing, the heart, or the reflex actions. Since this discovery, many physiologists--and I regret not to be able to say so of every physiologist--have given up curare and use nothing but chloralose, which is a perfect anæsthetic, and which allows the reflex actions to be studied although anæsthesia is perfect.