Abstract: Apparatus for removing liquified gas which boils at ambient temperature from an enclosed reservoir. Removal from the reservoir is controlled by an on-off valve disposed in a delivery line, while selectively venting the pressurized vapor of the liquid generated above the reservoir. When flow is desired, the valve is opened and the vent is blocked by a warm heat rod slidable into and out of heat exchange relation with the liquid in the reservoir, which causes the liquid to boil and consequently, increases the vapor pressure on the liquid to cause it to flow through the delivery tube.

Abstract: A method and apparatus for measuring the temperature of malignant tissue to be frozen during cryosurgery, involving the insertion of an active needle electrode (18) laterally of and below the malignant tumor (T or T') to be treated, applying an indifferent electrode (20) to the patient's skin (S) at a point displaced from the tumor, applying a low voltage D.C. potential (12) across the electrodes to pass a current of less than 20 microamperes through the tissue, and monitoring (16) the current decrease during freezing to determine the point at which to terminate the freeze treatment with cryocongelation of all the malignant tissue but without substantial destruction of the underlying tissue.