Excerpt from The American Journal of Physiology, 1909-1910, Vol. 25 The investigations of Haldane and his co-workers demonstrate that in normal life the co2 content Of the blood is maintained within very narrow limits Of variation. This regulation depends upon the unvarying level and the sharpness of the threshold (i. E., the sensitiveness) Of the respiratory centre for co, . A slight diminution in the co. Content of the arterial blood produced by a few forced respirations automatically induces apnoea. The addition of per cent Of co. To the air breathed doubles the respiratory activity. Day and night, year after year, the threshold is the same.xiv Proceedings of {he A'n-zerican Physiological Society. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.