COBRA, the name applied to the poisonous Colubrine snakes of the genera Naja and Sepedon which have the power of dilat ing the neck laterally to form a broad disc or "hood." The dilata tion is brought about by the raising and pushing forward of the long anterior ribs, the elastic skin being stretched taut over the framework which they form. This type of hood is in marked con trast to the vertical expansion of the neck which many snakes (e.g., boomslang and mamba) can produce and which is caused by the inflation of the wind-pipe. In all species, however, erection of the hood only occurs when the animal is annoyed or disturbed.
The genus Naja, containing about ten species, ranges from the Cape throughout Africa, Arabia and India to southern China, the Philippine islands and the Malay Archipelago ; Sepedon, with a single species, is confined to South Africa. Both genera are pro teroglyphous, i.e., with fixed poison fangs on the front of the upper jaw, and the bite of all the species is extremely dangerous. Accurate statistics of snake-bite mortality cannot be obtained, but it seems fairly certain that the common Indian cobra (Naja naja tripudians) is responsible for several thousand deaths an nually. This regrettable state of affairs is due to several causes. As in all proteroglyphous snakes the venom acts directly on the nervous system and so is much more rapid in its action than that of the viperine and opisthoglyphous snakes, the toxicity of which is chiefly due to its power of destroying the blood corpuscles. In the past, despite a multitude of so-called cures and a widespread belief in the efficacy of "snake stones," no really effective treat ment was available except immediate excision of the site of the bite; now efficient "anti-venines" are produced from the blood sera of animals which have been immunized by regulated doses of venom. These anti-venines, however, must be administered hypo dermically, the dose is large and to be effective for the bites of proteroglyphous snakes must be given immediately, conditions not easily obtained in most of the regions which cobras inhabit. Again, the food of these snakes consist chiefly of frogs, toads, small mammals and, less frequently, birds, and the prevalence of rats and mice frequently attracts them to the vicinity of vil lages and houses where they are more likely to come into contact with man. In India also, cobras are often regarded with so much superstitious reverence that no attempt is made to kill them.
The best known species is the common Indian cobra (Naja na ja tripudians), which may reach a length of about 51 f t. and which exhibits great variation in colour ; typically it is yellowish to dark brown with a black and white spectacle-shaped marking on the hood, but all gradations between this form and specimens without any trace of such a mark are known. The king cobra or ham adryad (Naja hannah bungarus) is another oriental species ; it is rarer than the common cobra, larger, reaching a length of about 12 ft., and feeds chiefly on other snakes. Like all the cobras it lays eggs, but unlike them, exercises some parental care; a definite nest of dried leaves is made and the parents remain in the vicinity of the nest until the eggs are hatched. In Africa there are several species, the hooded or Egyptian cobra (Naja ha je) and the black-necked cobra (Naja nigricollis) being the most widely distributed. The spitting cobra or ringhals (Sepedon haemachaetes) is closely allied to the true cobras (Naja) and is notorious for its habit of "spitting" venom when annoyed. The mechanism of this "spitting" appears to be that by compression of the poison-glands the venom is forced out through the fangs and at the same time a blast of air is exhaled. This carries the liquid forward as a spray for a considerable dis tance and if it strikes a person in the eyes intense irritation is set up which results in temporary, and sometimes permanent blindness. (D. M. S. W.)