PROPERTIES OF THE BLOOD OF THE SKATE (RAIA OSCILLATA)

¹ From the Fatigue Laboratory, Morgan Hall, Harvard University, and the Marine Biological Laboratory, Woods Hole, Mass.

In the acid range, carbon dioxide pressure has almost no effect on affinity of skate's whole blood for oxygen. In the physiological range the effect is appreciable but still only one-half as great as in man. No difference was discerned between the carbon dioxide dissociation curves of oxygenated and of reduced blood. This was partly due to the facts that the hemoglobin concentration is one-fourth as great as in man and that the carbonic acid-combining capacity (when pCO₂ = 40 mm.) is less than in man.

The effect of temperature on the oxygen dissociation curves is identical with that found by Brown and Hill (1923) for human blood but somewhat different from that found by Redfield and Florkin (1931) for Urechis blood.

The buffer value of plasma proteins is about twice as great, per unit weight, as that of human plasma proteins. Since the concentration f protein in skate's plasma is one-third to one-half as great as in human plasma, it follows that the buffer value of plasma of the two species is about the same. Buffer value of whole blood is nearly equal to that of human blood of the same oxygen-combining capacity.

Transfer of gases between the blood and the external medium takes place under conditions which are quite different from those in the lungs of man. Nevertheless arterial blood is about equally saturated with oxygen in the two species. The absolute values for carbon dioxide pressure in man and the skate are very different because the blood of the skate is exposed to a virtual vacuum in respect to carbon dioxide. The pressure head of carbon dioxide from blood to the external medium, however, is of the same order of magnitude, about 1 mm. in each species. The supposition that there is a steep pressure gradient in respect to carbon dioxide in such a marine species as the skate is incorrect.