III. CIRCULATION. In such a body the heart would beat 75 times a minute, and probably drive out, at each stroke from each ventricle, from 5 to 6 cubic inches, or about 1,500 grains of blood. The blood would probably move in the great arteries at a rate of about 12 inches in a second, in the capillaries at I to inches in a minute; and the time taken up in performing the entire circuit would probably be about 30 seconds. The left ventricle would probably exert a pressure on the aorta equal to the pressure on the square inch of a column of blood about 9 feet in height; or of a column of mercury about 9 inches in height; and would do in 24 hours an amount of work equivalent to about 90 foot-tons ; the work of the whole heart being about 120 foot-tons. IV. RESPIRATION. Such a body would breathe about 17 times a minute. The lungs would contain of residual air about 100 cubic inches, of supplemental or reserve air about 100 cubic inches, of tidal air 20 to 30 cubic inches, and of complemental air 100 cubic inches. The vital capacity of the chest-that is, the greatest quantity of air which could be inspired or expired—would be about 230 cubic inches. There would pass through the lungs, per diem, about 350 cubic feet of air. In passing through the lungs, the air would lose from 4 to 6 per cent. of its volume of oxygen, and gain 4 to 5 per cent. of carbonic acid. During 24 hours there would be consumed about 10,000 grains oxygen; and produced about 12,000 grains carbonic acid, corresponding to 3,300 grains carbon. During the same time about 5,000 grains or 9 oz. of water would be exhaled from the respiratory organs. In 24 hours such a body would vitiate 1,750 cubic feet of pure air to the extent of 1 per cent., or 17,500 cubic feet of pure air to the extent of 1 per 1,000. Taking the amount of carbonic acid in the atmosphere at 3 parts, and in expired air at 470 parts in 10,000, such a body would require a supply per diem of more than 23,000 cubic feet of ordinary air, in order that the surrounding atmosphere might not contain more than 1 per 1,000 of carbonic acid (when air is vitiated from animal sources with carbonic acid to more than 1 per 1,000, the concomitant impurities become appreciable to the nose). A man of the weight mentioned (11 stone) ought, therefore, to have at least 800 cubic feet of well-ventilated space. V. CUTANEOUS EXCRETION. Such a body would throw off by the skin—of water about 18 ounces, or 10,000 grains; of solid matters about 300 grains; of carbonic acid about 400 grains, in 24 hours. VI. RENAL EXCRETION. Such a body would pass by the kidneys-of water about 50 ounces; of urea about 500 grains; of other solid matters about 500 grains, in 24 hours. VII. NERVOUS ACTION. A nervous impulse travels along a nerve at the rate of about 80 feet in a second in the frog, and of about 100 feet a second in man; but the rate in man varies very much according to circumstances. VIII. HISTOLOGY. The following are some of the most important histological measurements : Red blood-corpuscles, breadth 7 μ to 8 μ. White blood-corpuscles, breadth 10 μ. ʊth of an inch, or ʊʊth of an inch, or th of Striated muscular fibre (very variable), breadth an inch, or 60 μ; length 1 inch, or 30 to 40 millimetres. Non-striated muscular fibre (variable), breadth 1oooth of an inch, or 6μ; length both of an inch, or 50 μ. B B Nerve fibre (very variable), breadth 10th to th of an inch, or 2 μ to 12 μ. Nerve cells (of spinal cord) excluding processes, breadth Both tooth or more of an inch, 50 μ to 100 μ or more. Fibrils of connective tissue, breadth 50th of an inch, or I μ. Superficial cells of epidermis, breadth oath of an inch, or 25 μ. Capillary blood-vessels (variable), width ʊʊth to gʊʊʊth of an inch, or 7 μ to 12 μ. Cilia, from the wind-pipe, length south of an inch, or 8 μ. Cones in the yellow spot of the retina, width south of an inch, or 3 μ. |