THE RESPIRATORY FUNCTION OF THE BLOOD OF URECHIS CAUPO

Abstract

The blood of U. caupo contains hemoglobin enclosed in corpuscles. Its 0 capacity is 2.66-7.22 volumes % and the percentage of cells 18-40. The O and CO2 dissociation curves are measured. The position of 0 curves does not appear to be influenced by CO2 pressure nor is the ability of the blood to combine with CO2 influenced by the degree of oxygenation of the blood. The effect of temp. upon the 0 curve is similar to that observed in other bloods. The buffer value of the blood is 11 volumes % over a considerable range of CO2 pressures and is accounted for by the concentration of hemoglobin. The concentration of CO2 is about equal in corpuscles and plasma. The plasma contains a negligible quantity of buffer. With increased CO2 tension there is a small but limited exchange of material between corpuscles and plasma which increases the ability of the plasma to combine with carbonic acid. The hemoglobin in vivo is almost completely saturated. The CO2 content in vivo is 7 to 9 volumes %, corresponding to a CO2 pressure of about 7 mm. Hg. The reaction of the blood is estimated to be about pH 7.1. The ventilation of the hind gut is considered quantitatively, the result indicating that the respiratory activity is nicely adjusted to the metabolic requirements. The function of hemoglobin and its relation to the O supply during low tide are discussed. It is suggested that the movement of water within the flats due to changing tidal level is important in supplying O when the tide is out.