The lungs of snakes, then, are supplied with air through that moveable tube, and the ‘glottis,’ which is the mouth or opening of what may here be called the air-tube, not to venture on scientific terms, was what I had seen ‘puckered up,’ as it appeared. We may briefly remind the reader that our own throats contain two passages, one to the lungs, the other to the stomach; and in order that the air passage may be safely guarded from the entrance of any foreign particles, there are various parts, valves, and muscles which come into play with the action of swallowing, each and all having technical names, larynx, pharynx, glottis, epiglottis, etc., which need not be here described. But in the adaptive development of those wonderful creatures, snakes, the entrance or mouth of the windpipe—which begins _in_ their mouth—can not only be closed at will, but still further to protect the passage, and also to enable the reptiles to breathe during the long process of swallowing, they can absolutely bring the apparatus forward, even _beyond_ their mouths; and this was what had so surprised me on witnessing it. The glottis, being the soft, membranous end or aperture, was what opened and closed, expanded and contracted, by that sort of puckering up and loosening again that was observable, and which here was rounded, but in the higher animals is a narrow, lip-like slit. Some physiologists, in describing this ‘air-tube’ of serpents, speak of it as the _larynx_, which is what we unscientific folk would call the entrance to, or the upper portion of, the true windpipe or trachea. Others, again, affirm that they saw the ‘windpipe’ projecting. After all, much less has been said about it than one could wish; and what is said is somewhat conflicting, perhaps on account of the obscurity connected with this surprising adaptation of means to necessities. A thorough examination of the position of the trachea of snakes _while feeding_, and a perfect realization of its functions, could only be obtained were it possible to arrest the process of feeding by the instantaneous death of the feeder, and while every muscle of the snake’s mouth remained in position. Even then, one could not be positive, as snakes are endowed with the astonishing power of carrying out their intentions, or, in common language, ‘going on with their business,’ even after death. That is to say, owing to the irritability of their muscles, the action which they were about to perform (as, for instance, springing at a foe) continues should the head be shot off at the moment of making the attempt. In p. 56 and chap. xxi. some remarkable elucidations of this are given.