The general appearance of a windpipe is familiar to every one. It is formed of a series of rings or hoops, partially cartilaginous in mammals; that is to say, they are incomplete behind, where their ends are united by muscle and membrane, and come in contact with the gullet; but in serpents the rings are entire, the ends of each being joined together by an elastic substance. The rings themselves are also connected with each other by elastic membranes, so that the windpipe is capable of being extended like an india-rubber tube, and of regaining its former position. The length of it naturally varies according to the size and species of serpent; but as a rule it is always much longer comparatively than in man. In a full-sized rattlesnake, the trachea is about twenty inches long. In a boa constrictor, also, though a much larger snake, it measures about the same. In smaller snakes it is, of course, much shorter; but there is the same singular diversity in this as we find in other serpent anomalies, viz. a great variation in the length in snakes of equal size, and without any very apparent reason. Bingley, in his _Animal Biography_, 1820, describes the appearance of a large snake (M’Leod’s celebrated boa) when gorging a goat; but the account, like those of that time, is more sensational than scientific. ‘His cheeks were immensely dilated, and appeared to be bursting, and his _windpipe_ projected three inches beyond his jaws.’ Broderip, a few years later, 1825, more lucidly and dispassionately describes what he had observed. ‘I have uniformly found that the larynx is, during the operation of swallowing, protruded sometimes as much as a quarter of an inch beyond the edge of the dilated lower jaw. I have seen, in company with others, the valves of the glottis open and shut, and the dead rabbit’s fur immediately before the aperture stirred, apparently by the serpent’s breath, when his jaws and throat were stiff, and stretched to excess’ (_Zoological Journal_, ii. 1826). This account is quoted from the paper entitled, ‘Some Account of the Mode in which the Boa Constrictor takes its Prey, and of the Adaptation of its Organization to its Habits,’ by W. J. Broderip, Esq., F.L.S. The paper was written as a criticism of the M’Leod story. I, also, on several occasions, saw the fur or feathers stirred by air when the mouth or valve opened of what we may safely call the _air-tube_, whether larynx or trachea.