Determination of pH of Living Tissue by the Glass Electrode. ∗

Abstract

The ordinary bulb type of glass electrode is necessarily limited in its use for determining the hydrogen-ion concentration of living tissues to fluids or to cavities in which such an instrument can be placed. For example, the pH of the blood can be determined by actual insertion of the electrode in some of the larger vessels, or the blood stream can be diverted into a chamber surrounding the glass bulb. Other determinations of the pH of living tissue have involved the actual destruction of that tissue, regardless of whether the colorimetric method, or the hydrogen, the quinhydrone, or the glass electrode was used. We have employed a spear type of capillary glass electrode which can be inserted directly into the tissues; in this series of experiments, into the intestinal wall of the white rat. The vacuum tube amplifying system used was essentially that described by DeEds. 1 The electrodes were drawn of Corning No. 015 glass, and were from 30μ to 100μ in thickness, the capillary wall varying from 10μ, to 30μ. They were filled with 1/10 N HCl saturated with quinhydrone, sealed at the tip, and calibrated at the temperature of the tissue just before and immediately after using. The animal was completely insulated, being in contact only with the tip of the glass electrode and with the end of the calomel half cell. The latter was inserted into the peritoneal cavity of the rat, which was kept under ether anesthesia throughout the experiment; a portion of the intestine was fastened to an upright slab of hard rubber; an incision was made in the wall of the gut and a reading taken at once, care being taken to prevent loss of heat.