In the course of experiments involving the perfusion of liver and kidney, a need arose for an oxygenator which was capable of oxygenating small as well as large volumes of blood with equal efficiency and which minimized the contact of circuiting blood and foreign matter. Because of this need, a new type of oxygenator was designed. The basic design of the "disk" oxygenator is used, in which disks rotate vertically in a blood-filled, cylindrical vessel, except that, in the present case, the vessel is a spherical bowl and the disks rotate at an angle of 45[degree]. This new design has the following advantages: a) the surface of the disks and the number of disks exposed to the circulating blood increase with increasing blood volumes so that the same efficiency of oxygenation is achieved with small (7 ml) and large (80 ml) blood volumes; b) no joints come in contact with circulating blood, thus avoiding leakage or contamination with grease; c) oxygen is utilized efficiently because the flow of oxygen is channeled from the inlet alongside the rotating disks. The oxygenator consists of 2 hemispherical bowls of Pyrex glass, each measuring 9 cm across its largest circumference. Each bowl is equipped with a ground-glass rim for the purpose of joining snugly the two bowls. The lower bowl is held in place by a ring; the upper by a clamp. Alternatively, the 2 bowls may be kept together by a large pinch clamp.