At the base is the 'cricoid cartilage,' the support and bond of union of the rest. Above are the 'arytenoid cartilages,' resting on the 'chorda vocales' and influencing their action. The 'epiglottis' is placed at the extremity of the opening into the windpipe, with its back opposed to the pharynx, so that when a pellet of food passes from the pharynx in its way to the oesophagus, the epiglottis is applied over the glottis, and by this means closes the aperture of the larynx, and prevents any portion of the food from passing into it. The food having passed over the epiglottis, that cartilage, from its elastic power, again rises and resumes its former situation. The 'thyroid cartilage' envelopes and protects all the rest, and particularly the lining membrane of the larynx, which vibrates from the impulse of the air that passes. The vibrations spread in every direction until they reach the delicate membrane of the tympanum of the ear. That membrane responds to the motion without, and the vibration is carried on to the pulp of the auditory nerve, deep in the recesses of the ear. The loudness of the tone--its acuteness or graveness--depends on the force of the expired air and the shortening or lengthening of the chord. Hence it is, that the tone of the bark of the dog, or the neighing of the horse, depends so much on the age or size of the animal. Thus we compare the shrill bark of the puppy with the hoarse one of the adult dog; the high-toned but sweet music of the beagle with the fuller and lower cry of the fox-hound, and the deep but melodious baying of the mastiff. I may, perhaps, be permitted to add to these, the whinnying of the colt and the neighing of the horse. Each animal has his peculiar and intelligible language. He who has long lived among them will recognise the tone of delight at meeting, rising into and terminating in a sharper sound; the strong and elevated tone when they are calling to or challenging each other at a distance; the short expression of anger--the longer, deeper, hoarser tone of fear; the murmur almost as deep, but softer, of habitual attachment, and the elevated yet melodious token of sudden recognition. I could carry on a conversation with a dog that I once possessed for several minutes, and one perfectly intelligible to both.