Thus, _Dasypeltis_ eats nothing but birds' eggs, the shells of which are crushed in the gullet, by a special contrivance mentioned above (p. 80), and are soon after rejected through the mouth as a pellet. Other snakes, such as _Coluber_ and _Lioheterodon_ show themselves partial to eggs in addition to live prey, but their alimentary canal does not depart from the normal, the eggs being broken in the stomach and the remains of the shells passed with the excrements. The Amblycephalidæ subsist almost entirely on snails and slugs, the shells of the former being crushed in the anterior part of the intestine after their contents have been digested, and the débris are rejected through the vent. A small land tortoise has been found in the stomach of a Cobra (_Naia haie_) from Algeria. Snakes which take large prey secure it according to three methods: By catching it simply with the jaws, and immediately proceeding to swallow it, as in _Tropidonotus_ and in some of the Constrictors when dealing with small animals; by constriction, after having seized it with the jaws, crushing it in the coils of their body and thus killing it previous to feeding, as in the Boidæ and _Coluber_; or by poisoning, by a mere stroke with the fangs, the result being awaited before the meal is begun, as in most of the Viperidæ. Other poisonous snakes proceed according to the first method, the use of the venom being to reduce the struggles of the victim and to relax its muscles. Such snakes as are in the habit of previously killing their prey show little reluctance to accept dead food in confinement, a thing which others usually refuse to do; they may, however, be deceived by the dead animal being agitated before them, and the system now adopted in our Zoological Gardens, of offering all snakes previously-killed animals, has been attended with comparative success. Some species feed almost exclusively on other snakes, and often manage to swallow individuals as large as, or even a little larger than, themselves. Examples are known of harmless snakes showing a predilection for dangerous species, to whose poison they are immune (see p. 71). As a rule snakes that eat fish will also eat batrachians, but nothing higher in the scale, although exceptions have been reported, such as the Anaconda feeding on mammals, birds, reptiles, and fish, and our Grass-snake having taken mice and birds. Some that feed chiefly on lizards and snakes will occasionally eat also mammals, and _vice versa_, but rarely frogs. On the other hand, European Vipers accommodate themselves to a more varied bill of fare, being known to feed on mammals, birds, reptiles, batrachians, insects, and slugs, and they have even been observed to eat voles showing signs of putrefaction.