The true structure and mode of formation of the poi son fangs, appear to have been lirst investigated with care by Smith. Ile found that the poison tube was form ed by a fold on the sm face, the edges of which met in the middle, but continued separate at the point and base. The hollow in the middle of the tooth in which the se creting pulp was situated, can easily be traced as un connected with this tubular external fold. The same observer found several of the common teeth having the rudiments of this external groove. (Mr. Smith On the Structure of the P 0i807201a Fangs uf Serpents. Phil. Trans. 1818,p. 471) It is usually supposed, that upon the first ritilgb being desuoyed, others are developed to supply their place. There is, however, some difficulty in accounting lor the manner in which the poison duct, in such cases, can change its course. It is probable, that the grooves in the adjoining common teeth have given rise to the opinion. More accurate observation, how ever, can alone determine the point.
The poison itself has much the appearance of oil ; but in its general properties it resembles gum. Its noxious qualities continue even after it is dried.
From the structure of the fangs, the poison is instil led into the bottom of the wound, and if in any quantity it enters any of the larger vessels, death speedily fol lows. In other cases, thcre is previously great pain produced ; the part swells and becomes discoloured, and exhibits marked indications of violent local action.
The virulence of the poison depends not only on the species of serpent, but on its condition at the time, and the habit of body of the animal which has received the bite.
The remedies which have been suggested to destroy the influence of the venom alter the bite, are numerous, but few of them can be safely, relied on. Some recom mend making an incision into the part wounded by the fangs, and sucking, out the venom and contaminated blood. Others advise the unfortunate patient to com press the part by ligature, and thus, by retarding the circulation, give time for the poison to hccome diluted and neutralized by the local fluids.. These remedies are obviously, such as in ordinary cases should be resorted to. On the other hand, some recommend the intetnal and external use of ammonia, the external application of caustic potash, or of heated turpentine. Alany ve getables have likewise been employed as antidotes. The subject, however, though ooe of great interest, is in some measure unexplored, and can only receive useful illustration front the researches of those who reside in the districts where the larger and tnore venomous species so frequently prove destructive to human life.
The tongue is usually slender, divided at the extre mity, and sheathed at the base. The alimentary canal is short in proportion to the size of the body. The gullet and stomach are capable of great dilatation, to receite the large animals which are swallowed. Di gestion takes place slowly. The liver is in general uniform in its appearance, and nearly entire. The gall bladder is present. The spleen is of a lengthened form, and placed at tile commencement of the intestines.
The heart possesses two auricles, and one ventricle. The portion of blood transmitted for xration, is return ed by a systemic vein to the systemic auricle, from which it passes into the common ventricle, which re ceives through the other auricle the blood returned from the body.
All serpents breathe air. Though many species can dive, they are compelled to return at intervals to the sur face ol' the water in order to respire. The larynx is too simple and inembranaceous, to admit of the existence or voice. A hissing. sound, however, can be produced. The trachea is a membranaceous tube, terminating di rectly in the lungs without the usual bronchial divisions. The lungs are single, in the form of an e:oogated bag,, with large cells on the walls. This bag lies in the ca vity of the abdomen.
The. kidneys are lengthened and labulated. The ureters termitiate usually by a single orifice in the cloaca, in the form of a papilla, directed towards the bag, which muy be considered as the bladder of urine. 'Fills bladder is formed by a fold of the coats of the in testine: it receives the contents of the ureters unmixed with the fiEces.
In this receptacle, the urine frequently becomes in spissated, and is voided in lumps at distant intervals, which have frequently been mistaken for fxces. In its ordinary state, Dr. John Davy, to whom the public is indebted for several valuable observations on the urinary organs of the amphibia, (Phil. Trans. 1818, p. SO4.) describes it as of a butyraceous consistence, becoming hard, like chalk, by exposure to the air, and consisting of pure uric acid.
The repioductive organs of serpents present few pe culiarities. The external organs of the male are double, each short, and surrounded with bristles. These, in the rattlesnake and viper, are bifid, attd beset with bristles. They appear in a pouch near the anus. In the female the external openings are double, corresponding. with the conditions of the male organs. Impregnation takes place internally. Some species are oviparous, others are ovoviviparous. The young- do not undergo any re markable metamorphosis.