22 THE SCIENTIFIC MONTHLY
phere as an inexhaustible reservoir of carbon, only slightly depleted by the drafts made upon it by the action of chlorophyllic plants or by its solution in the waters of the continents and oceans. Soluble in water and thus equally mobile, of high absorption coefficient, and of universal occurrence, it constituted a reservoir of potential energy for the de- velopment of plants and animals. Carbon dioxide in water forms car- bonic acid, one of the few instances of biological decomposition of water. This compound is so unstable that it has never been obtained. Carbon dioxide is now produced not only within the atmosphere but also by the action of certain anaerobic bacteria and molds without the pres- ence of free oxygen, as, for example, through the catalytic action of zymase, the enzyme of yeast, which is soluble in water. Loeb°^ dwells upon the importance of the bicarbonates as regulators in the develop- ment of the marine organisms by keeping neutral the water and the solutions in which marine animals live. Similarly the life of fresh- water animals is also prolonged by the addition of bicarbonates.
Thus from the chlorophyllic stage onwards the compounds of carbon, hydrogen, and oxygen (C, H, 0)'* constitute a unique ensemble of fitness among all the possible chemical substances for the exchange of matter and energy both within the organism and between it and its environment. The regulator'^ or ^* balancing^' influence is exerted by the phosphates and upon the acidifying tendency of carbon dioxide. The carbon dioxide in respiration raises the hydrogen concentration of the blood. The phosphates restrain this tendency while the breathing apparatus, in response to stimulus from the respiratory center irritated by the hydrogen, throws out the excess of the latter.
ei Loeb, Jaeques, 1906, pp. 96, 97.
«3 Henderson, Lawrence J., 1913, pp. 71, 194, 195, 207, 231, 232.
{To he continued)
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