The student of physiologic functions can scarcely fail to be impressed by the nicety with which certain chemical reactions in the organism are conducted. Perhaps the most conspicuous instance of this is represented by the neutrality regulation whereby the blood maintains its remarkable fixity of reaction. According to Myers and Booher,7 for example, the normal range of pH for the blood probably lies between 7.35 and 7.43, values lower than 7.32 and higher than 7.47 being definitely abnormal. The maximum tolerated range is said to lie between pH 7.0 and 7.8. To preserve this type of "normality" a variety of corrective or compensatory devices are at the disposal of the organism.
Resistance to changes in hydrogen ion concentration is brought about by buffer action. A buffer has been compared to "a sponge having the capacity of 'soaking up' hydrogen and hydroxyl ions." The buffers of the blood