Improved Form of Electrical Drop — Recorder

Abstract

THE drop-recorder here described is a modified form of that used in the Physiological Laboratory of the University of Edinburgh. It consists of a fine steel spring S, to the free end of which is attached a disc D with the convex side uppermost on which the drops fall. Terminals T1 and T2, in circuit with a battery and recording electro-magnet, are insulated from each other by the vulcanite block V; contact is made and the circuit closed when the spring touches the platinum-tipped adjustable screw P, that is, by drops falling on the disc. A strip of brass B, controlled by another adjustable screw R, acts as a damper on the spring to prevent afteroscillation. When the secretion, such as bile or saliva, whose rate of flow is being recorded, contains much mucin, it may now and again cause the damper to stick to the spring; to prevent this the disc is made with a small up-turned tongue piece T, which guards the end of the damper. The adjustment is most easily rnade when the damper acts on the spring close to the disc.The vulcanite block V of the recorder is fixed to the lower end of a rectangular piece of brass or band-iron A to which is riveted a stand clamp F. The horizontal limb of this rectangular piece has two holesone vertically over the disc D to receive the small brass tube E connected by means of rubber tubing to the cannula in the duct of the organ under experiment, the other to hold a reservoir of water W. The distance between the end of the horizontal arm and the disc D is about 8 inches, and the brass tube can be adjusted to any suitable height and afterwards held in position by the screw G.Just before the recorder is to be used the outflow tube E is replaced by the reservoir W, and by means of the small stopcock C, water is allowed to fall in drops on the disc, so that the necessary adjustments of the screws P and R can be made without causing any delay at the beginning of an experiment. Wheni this is done, the reservoir is removed and the outflow tube fixed at the same height.A ring-support for a beaker to catch the drops is also very convenienlt.