Polygraph

POLYGRAPH, an instrument for recording simultaneously multiple curves. It consists of a clock mechanism that drives a smoked paper strip approximately 75 mm wide. On this strip, three Mareev's small drums write with their pens, arranged in a line perpendicular to the length of the strip. The fourth recording is the registration of time intervals of 1 sec. and 0.2 sec. The P. is convenient in that compared to the kymograph, it is quite portable and fits into a case the size of a microscope case. The P. is used when it is necessary to record three simultaneously occurring processes, for example, the pulse in the a. carotis, a. brachialis, and respiration. Points on the curves lying on the same line correspond to the same moments in time. A disadvantage of the P. is the narrow width of the paper strip, due to which all curves have very small amplitude. Sometimes the P. is part of another instrument and is accordingly modified, which is the case, for example, in Uskov's sphygmomanometer. The P. has wide application in physiology and clinical practice, and with its help numerous studies of simultaneous phlebography and sphygmography have been conducted.