If the function of oxygen in common air is to set free in the blood, either in the capillaries alone, or throughout the whole of the arterial circulation, carbonic acid gas; and that it cannot escape from the system unless it do so in the lungs as it passes in the general current--except a trace that is removed by the skin and kidneys--and that the quantity of carbonic acid gas set free is in exact relation to the amount of oxygen taken into the blood, what effect _must be_ manifested where one hundred respirations in one minute are made--five or six times the normal number--while the heart is only propelling the blood a very little faster through the lungs, and _more feebly_--say 90 pulsations at most, when to be in proportion it should be 400 to 100 respirations to sustain life any length of time? You cannot deny the fact that a definite amount of oxygen can be absorbed and is absorbed as fast as it is carried into the lungs, even if there be one hundred respirations to the minute, while the pulsations of the heart are only ninety! Nature has _made it_ possible to breathe so rapidly to meet any emergency; and we can well see its beautiful application in the normal action of both the heart and lungs while one is violently running. What would result, and that very speedily, were the act of respiration to remain at the standard--say 18 or 20--when the heart is in violent action from this running? Asphyxia would surely end the matter! And why? The excessive exercise of the whole body is setting free from the tissues such an amount of excretive matter, and carbon more largely than all the others, that, without a relative action of the lungs to admit the air that oxygen may be absorbed, carbonic acid gas cannot be liberated through the lungs as fast as the waste carbon of the overworked tissues is being made by disassimilation from this excess of respiration. You are already aware how small a quantity of carbonic acid in excess in the air will seriously affect life. Even 2 to 3 per cent, in a short time will prove fatal. In ordinary respiration of 20 to the minute the average of carbonic acid exhaled is 4.35. From experiments long ago made by Vierordt--see Carpenter, p. 524--you will see the relative per cent, of carbonic acid exhaled from a given number of respirations. When he was breathing six times per minute, 5.5 per cent of the exhaled air was carbonic acid; twelve times, 4.2; twenty-four times, 3.3; forty-eight times, 3; ninety-six times, 2.6. Remember this is based upon the whole number of respirations in the minute and not each exhalation--which latter could not be measured by the most minute method.