In process of dissection, he detected two muscles in the lower jaw, evidently intended for the purpose of bringing the larynx forward; how far forward and how much of the true windpipe was also brought forward, he did not say. But this in a dead specimen could scarcely be affirmed with certainty. From the large size of their prey, and the jaws being stretched open and gorged to their utmost capacity, it is plain that snakes cannot breathe freely in the ordinary manner while feeding, a process sometimes of an hour or more. Owing to the construction of their lungs and their capability to contain a large volume of air, they do not require to breathe frequently; still they do occasionally take a fresh inspiration, and their needs are met by this wonderful arrangement of the breathing apparatus. [Illustration] [Illustration] CHAPTER IX. _BREATHING AND HISSING OF SNAKES._ FOLLOWING on the subject of the last chapter comes that of respiration; and in connection with breathing is the ‘voice,’ so far as this class of animals can be said to possess a voice. As already seen in the description of the glottis, serpents do not breathe in the ordinary way, with short and regular inspirations, but when they do respire, they take in a supply of air to last them for some time. Their lungs, instead of occupying one particular portion of the body corresponding with the chest of the higher animals, are less developed. One lung—or what Professor Owen calls the long pulmonary bag—of snakes extends along more than half of their body; in some species nearly to the anus. Only one lung is normal, the other is rudimentary. The circulation is so arranged that on each contraction of the heart only a part of the blood is exposed to the influence of the air and becomes oxygenated, the rest returning to the parts without having undergone the action of respiration at all. The blood is, in consequence, poor in red corpuscles, its circulation is comparatively languid, the reptile becomes easily torpid, and its temperature is influenced by the surrounding atmosphere more than by the vigour of its own functions. This is why, when not excited to activity by external warmth, reptiles can pass a long time without food. Having no fixed temperature to maintain, one important source of demand for food is withdrawn.