At the Institut Pasteur at Lille there is prepared in this manner an antivenomous serum from the horse; it is capable of acting upon 20 000 times its own weight. This has rendered great service in the treatment of snake-bites, particularly in hot countries, where the accidents are of daily occurrence. _In vitro_ it acts quite as well preventively as therapeutically. It arrests the effects of the naja, the horned ceraste, the trigonocephalus, the rattlesnake, and of almost every one of the venomous serpents known. The relatively considerable immunity possessed by certain snake-charmers, and which passes for a magical gift, is due to nothing else but a natural immunity, acquired perhaps by heredity, and it always appears to follow as a result of a nonfatal snake-bite. =Venoms of Batrachians and Saurians.=--We observe here a fundamental difference between these poisons and those of snakes, as we shall see. These latter, in fact, appear to owe all their toxicity to true toxins which they contain, while the poisons of batrachians and saurians are chiefly composed of alkaloidal bases.[152] [152] CLOEZ: _Compt. rend. de l'Acad. des Sciences_, XXXIV, p. 592. The poison of toads and frogs (studied by Faust, Bertrand, and Physalix) is chiefly secreted by the glands of the subcutaneous tissues of these animals; it has but a very slight action on the unbroken skin, but it rapidly inflames the nasal and buccal conjunctival mucosa. The poison is a yellowish liquid, milky and viscid, with a waxy odor and an insupportably bitter taste. It is strongly acid and caustic. When dried, the poison yields to ether a fatty matter which, when absorbed by an animal, plunges the latter into a coma that may end in death. The residue insoluble in ether contains the non-toxic albuminoids, and ptomaines, such as methylcarbylamine,[153] and isocyanacetic acid, resulting from the decomposition of a lecithin that appears to be soluble in ether. [153] _Ibid._, XCVIII, p. 538. To obtain this venom, Physalix and Bertrand[154] skin the toads, first chloroformed, and dry the skins in a vacuum over sulphuric acid; the skins are then cleaned by treating with carbon disulphide to remove fatty matters, and the toxic principles removed by means of 95-per cent. alcohol; the poison so obtained, however, is impure. A better procedure is to express the parotid glands which have been placed in distilled water. Faust found in this venom a principle which he named _bufonin_. Physalix and Bertrand isolated from it also a resinoid substance soluble in alcohol and in a large excess of water; this substance, which they named _bufotaline_, acts upon the heart. These authors have also obtained another substance which has a paralyzing action, and which they have named _bufotenin_. [154] _Ibid._, CXXVIII, pp. 45-48.