The enormous prey which some snakes are able to swallow is quite astounding. Anacondas and Pythons, the largest snakes, have been known to swallow calves and good-sized antelopes with their horns, animals which, even after being somewhat crushed by constriction, very much exceed the calibre of the snake. A _Python molurus_ 17 feet long is reported on good evidence to have swallowed a gravid Axis deer. A Grass-snake half an inch in diameter can manage a frog or toad three times that width, and a _Dasypeltis_ of the same size a hen's egg. Such feats are rendered possible by the mobility of the jaws and palato-pterygoid arch on the cranium, and the elasticity of the ligaments by which they are attached (see above, p. 42), as well as by the mobility of the ribs and the absence of sternal apparatus, together with the great distensibility of the skin. When a snake proceeds to dispose of a large prey, which, if it be a mammal or bird, is usually seized head-first, it pulls itself forward by alternate movements of the jaws, the maxillary and the mandibular ramus of the one side, and then of the other, being extended anteriorly and laterally, the snake at the same time producing an abundant salivation which renders the prey very slimy. Several repeated alternate movements of the jaws bring the head of the prey to the gullet, where the muscles and ribs come into play, and the two sides of the jaws work no longer alternately, but together. When once in the oesophagus, the prey progresses with much greater facility, and usually reaches the stomach in a few minutes, whilst the previous process of deglutition may have lasted half an hour. While this laborious operation is going on, the breathing of the snake is not impaired owing to a remarkable contrivance: the trachea can be protruded in such a manner as to bring its opening outside the mouth. In cases where the victim is eaten alive, the snake has to contend with its struggles, but retrogression is rendered impossible by the backwardly-directed sharp teeth with which the jaws and palate are beset. A frog is usually caught by one of the hind limbs and swallowed back-first, the long hind limbs stretching forwards as they fold against the body; its struggles are often still apparent when it has reached the oesophagus. Snakes when caught immediately after a meal are in the habit of disgorging their food, and it sometimes happens that a frog or toad is thus vomited alive. An instance is known of a naturalist having captured a Grass-snake and put it in a linen bag. On opening it a short time after, great was his surprise to find the snake had escaped through a small hole in the bag, leaving instead a living toad too big to pass through the hole.