Abstract

We have seen that epinephrine, histamine, barium chloride, nitrites and pituitrin have definite but different actions on blood concentration when injected alone or in 25 cc. of 0.8 per cent sodium chloride per kilo. Epinephrine, histamine and barium chloride decreasing the dilution of the blood with injections of salt solution and increasing the rate of return of hemoglobin to normal. Nitrites to some extent and pituitrin very definitely cause the opposite, a marked fall and a very slow return to normal of the hemoglobin curves. Besides the difference in action of these substances we are interested in the cause of these changes; whether there has been fluid loss or retention alone, or whether there has been a redistribution of red cells also. These experiments were undertaken to analyze the function, if any, of the hepatic veins in causing obstruction to blood flow and filtration of fluid into the liver tissue. On this account the changes and cause of change in venous pressures with these different drugs were taken up.

It will be seen that there is no relation between the hemoglobin concentration curves and the arterial pressure curves. This might be expected as capillary pressure curves do not run parallel with arterial pressures in all cases and one would not expect filtration of fluid through the thick arterial wall. It will however have been noticed that with the drugs causing an increase in venous pressure, epinephrine, histamine, barium chloride, that there is an increased rate of hemoglobin concentration while the nitrites and pituitrin neither of which causes an increase in venous pressure, cause no increased rate of hemoglobin concentration. This might be expected for any increase in venous pressure necessitates an increase in capillary pressure and in this way mechanically increases the tendency to filter fluid through the capillary walls. There are however exceptions to this observation.

In the cases where histamine and pituitrin, and also epinephrine and pituitrin, are mixed and injected together, there is an exception to the relationship between venous pressures and hemoglobin curves. Here in spite of the highest venous pressures recorded at any time, there is a very prolonged fall of the hemoglobin curve. Considering for a moment that a fall in the hemoglobin curve might be due to fluid loss one might expect that an increase in venous pressure would cause a loss of fluid through the thin walled capillaries in which there must be as great a pressure as in the veins. We have seen that there is this apparent loss of fluid when there is high venous pressure except in these two cases where pituitrin is given together with another drug. As pituitrin causes a prolonged fall in the hemoglobin curve, one might not expect fluid loss with this drug alone especially as there is no increase of venous pressure after its injection, but it is hard to conceive of an increase of pressure of 100 cm. of citrate without a filtration of fluid through the capillaries. A year or so after this observation was made Krogh (23) announced his discovery that pituitrin constricts the capillaries in the frog. It seemed for a time that in the cases here described with this high venous pressure either a change in the permeability of the vessels or a constriction of the capillaries reducing the filtration surface, were the chief factors to be considered, but the possibility of a redistribution of red cells had to be taken into consideration. There might be either a loss of fluid from the circulation or a storage of red cells. Considerable light was thrown on the possible action of pituitrin by the following experiment with ligation of the hepatic artery.