This venom, the physiological study of which was commenced by Dubosq, is an acid, opalescent liquid, hardly miscible with water. More complete experiments on this subject have been made by A. Briot,[122] who prepared a solution by sectioning the labium and poison-claws, and crushing the whole in physiological salt solution. When injected intravenously into rabbits, it produces immediate paralysis, with coagulation of the blood; subcutaneously it leads to the formation of enormous abscesses, with necrosis of the tissues. Small animals, such as spiders, species of _Scutigera_, beetles, &c., are very sensitive to it. The bite of _Scolopendridæ_ is very painful to human beings. In the Tropics such bites often cause somewhat serious results: insomnia, accelerated and intermittent pulse, and local œdema, which usually disappears after twenty-four hours. Well-authenticated fatal accidents have never been recorded (Bachelier,[123] Saulie[124]). (d) =Insects.= A very large number of insects produce acrid or irritant secretions, which serve them as a means of defence, but cannot be considered as true venoms; the species of _Meloë_ (oil-beetles) and _Cantharis_ (blister-beetles), are the most remarkable in this respect. The Order _Hymenoptera_ is the only one that includes a multitude of species really provided with poison-glands and an inoculatory apparatus. [Illustration: FIG. 99.--POISON-APPARATUS OF THE BEE. _gl.ac_, Acid gland and its two branches; _V_, poison-sac; _gl.al_, alkaline gland; _gor_, gorget. (After Carlet: figure borrowed from Hommel.)] The poison-organs, which have been well studied, especially by Leuckart,[125] Leydig,[126] Carlet,[127] and more especially by L. Bordas,[128] Janet,[129] and Seurat,[130] always include two and sometimes three kinds of glands: the _acid gland_, the _alkaline gland_ or gland of Dufour, and the _accessory poison-gland_ (fig. 99). The acid gland comprises a glandular portion (which sometimes takes the shape of a long flexuous tube, always bifid at its extremity, sometimes that of two tubes, simple or ramified, or again is composed of a bundle of cylindrical, simple or multifid canals), a poison-sac or reservoir, ovoid or spherical in shape, and an excretory duct, which is usually short. The alkaline gland, or gland of Dufour, exists in all Hymenoptera, and presents the appearance of an irregular tube, with a striated surface and a spherical or conical upper extremity. Its excretory duct opens, beside that of the acid gland, at the enlarged base of the gorget of the sting (fig. 100). [Illustration: FIG. 100.--INTERIOR OF THE GORGET OF THE BEE, SEEN FROM ITS POSTERIOR ASPECT. _cv_, Poison chamber; _gor_, gorget; _st_, stylet; _ca_, piston. Between the two stylets is seen the cleft _fa_, by which the air is able to enter into the air-chamber _cai_. (After Carlet: figure borrowed from Hommel.)]