Ventricular suction in the turtle.

In two different experimental environments the isolated turtle ventricle was found to fill and eject blood in the absence of a positive filling pressure. It is concluded that the ventricle can "suck" fluid using energy liberated from its wall during diastole. T HE question of ventricular "suction," that is "Does energy derived from the ventricle contribute to its filling in diastole?" has been debated from the time Erasistratus to the present and has recently been critically reviewed by Brecher. 1 A recent film and abstract by Bloom 2 offer support of the "suction" concept. The ultimate proof of suction as a physio-logic aid to filling should rest on a demonstration that, in the absence of a filling head, the ventricle develops a drop in intraventricular pressure which is sufficient to and actually does produce inflow. Because of the very low resistance of the A-V orifice the pressure difference necessary for inflow is very small and has not been measurable directly with existing apparatus except when inflow is impeded artificially. The pressure difference, then, must be inferred from the fact of flow. A positive filling head can be eliminated by the total immersion of the ventricle in fluid at any depth. In this way the filling head at any point within the heart chambers is exactly counterbalanced by the external pressure at that depth. In this way any inflow indicates that the heart wall has been instrumental in producing a lowering of intracardiac pressure and the consequent inflow of fluid. Two series of experiments on the excised ventricle of the turtle are here presented to throw light on this question. METHODS Series I. The heart was removed from a turtle and attached to a glass tube which passed through the cut atria into the ventricular cavity. A ligature tied into the atrioventricular groove and around the truncus aortac prevented fluid from entering or leaving the ventricle except through the tube (fig. 1A). This tube passed through a rubber stopper and was connected, by a short rubber connector bent at right angles, to a horizontal scrologic pipette. A duplicate pipette connected to a tube passing through the stopper was arranged parallel to the first but was not connected to the heart. These tubes were placed exactly level with each other to provide equal pressure inside and outside the ven-tricular wall. A bottle filled with Ringer's solution to the complete exclusion of air …