449. Observation had also assigned 12 pints of air as the volume constantly present in the lungs,—that is, 415.9108 cubic inches. The truth seems to be, that forty-eight times the quantity decomposed is constantly present, namely, 410.8926 cubic inches. The difference is only 4.0182 cubic inches, which difference weighs less than 1¼ grains troy. 450. It is then concluded that the real contents of the lungs is a volume of 410.8926 cubic inches, which is exactly the 540th part of 221,882 cubic inches, being the whole volume decomposed in twenty-four hours. But 160 seconds is also exactly the 540th part of the number of seconds in twenty-four hours. 451. Of the whole weight of oxygen consumed in twenty-four hours 15,757.9131 grains, the 540th part, or the proportion of 160 seconds, is 29.18132 “ and 410.8926 cubic inches of atmospheric air, which, as above, is the contents of the lungs, contain of oxygen the same weight 29.18132 “ 452. Then, if respiration were suddenly stopped, provision is made by the quantity of air always retained in the lungs for the oxygenation of the blood while flowing at the ordinary rate of 72 strokes per minute, for the exact space of 160 seconds, and for not one instant longer. 453. This interval of time, then, as has been stated (426), is very probably the time in which the blood performs one circuit, not 150 seconds. Then 540 circuits are performed in the twenty-four hours, or 3 circuits in every eight minutes. From this estimate has been deduced the quantity of blood contained in the whole body of the human adult (428). 454. The air inspired in twenty-four hours contains as under:— Bulk in Weight in Ingredients. cubic inches. grains troy. Undecomposed, and to be returned unchanged 665,646 205,758.833, Common air, To be decomposed, containing in solution { Pure atmospheric air 219,441 { 15,757.913, Oxygen, { { 52,294.509, Azote, { Vapour of water 2,219 428.726, Vapour, { Carbonic acid gas 222 105.130, Carbonic acid, Total 887,528 274,345.111, Of all kinds. This is, in bulk, 25,607¼ imperial pints, or 57 hogsheads, 1 gallon, and 7¼ pints, and in weight 571½ ounces and 25 grains. 455. Now, although the air expired, in consequence of its recomposition, may have undergone changes in bulk, yet it seems agreeable to all analogy to suppose that its weight will remain the same as the weight inhaled. This, however, is not asserted as a truth, but only assumed, in order to show the result of such a theory. 456. Then the air expired in twenty-four hours will be as follows:—