Instruments to facilitate in-vivo light transmission measurements.

Three instruments for making in-vivo light transmission measurements are described. They consist of a special holder for the photocell to be connected to the photometer, a fiber optic light guide to be connected to the illuminator, and the instrument itself which holds them together in a way so that the beam of light impinges directly on the photocell. A graded ruler, along with a vernier, make it possible to measure the thickness of the tissue as well.