THE LUNGS.—RESPIRATION.
2453. The first effect of air on the infant is a slight tremor about the lips and angles of the mouth, increasing to twitchings, and finally to a convulsive contraction of the lips and cheeks, the consequence of sudden cold to the nerves of the face. This spasmodic action produces a gasp, causing the air to rush through the mouth and nostrils, and enter the windpipe and upper portion of the flat and contracted lungs, which, like a sponge partly immersed in water, immediately expand. This is succeeded by a few faint sobs or pants, by which larger volumes of air are drawn into the chest, till, after a few seconds, and when a greater bulk of the lungs has become inflated, the breast-bone and ribs rise, the chest expands, and, with a sudden start, the infant gives utterance to a succession of loud, sharp cries, which have the effect of filling every cell of the entire organ with air and life. To the anxious mother, the first voice of her child is, doubtless, the sweetest music she ever heard; and the more loudly it peals, the greater should be her joy, as it is an indication of health and strength, and not only shows the perfect expansion of the lungs, but that the process of life has set in with vigour. Having welcomed in its own existence, like the morning bird, with a shrill note of gladness, the infant ceases its cry, and, after a few short sobs, usually subsides into sleep or quietude.
2454. At the same instant that the air rushes into the lungs, the valve, or door between the two sides of the heart-and through which the blood had previously passed-is closed and hermetically sealed, and the blood taking a new course, bounds into the lungs, now expanded with air, and which we have likened to a wetted sponge, to which they bear a not unapt affinity, air being substituted for water. It here receives the oxygen from the atmosphere, and the chyle, or white blood, from the digested food, and becomes, in an instant, arterial blood, a vital principle, from which every solid and fluid of the body is constructed. Besides the lungs, Nature has provided another respiratory organ, a sort of supplemental lung, that, as well as being a covering to the body, _in_spires air and _ex_pires moisture;—this is the cuticle, or skin; and so intimate is the connection between the skin and lungs, that whatever injures the first, is certain to affect the latter.
2455. Hence the difficulty of breathing experienced after scalds or burns on the cuticle, the cough that follows the absorption of cold or damp by the skin, the oppressed and laborious breathing experienced by children in all eruptive diseases, while the rash is coming to the surface, and the hot, dry skin that always attends congestion of the lungs, and fever.
2456. The great practical advantage derivable from this fact is, the knowledge that whatever relieves the one benefits the other. Hence, too, the great utility of hot baths in all affections of the lungs or diseases of the skin; and the reason why exposure to cold or wet is, in nearly all cases, followed by tightness of the chest, sore throat, difficulty of breathing, and cough. These symptoms are the consequence of a larger quantity of blood than is natural remaining in the lungs, and the cough is a mere effort of Nature to throw off the obstruction caused by the presence of too much blood in the organ of respiration. The hot bath, by causing a larger amount of blood to rush suddenly to the skin, has the effect of relieving the lungs of their excess of blood, and by equalizing the circulation, and promoting perspiration from the cuticle, affords immediate and direct benefit, both to the lungs and the system at large.