Plethysmograph \Pleth"ys*mo*graph\, n. [Gr. ? an enlargement +
-graph.] (Physiol.)
An instrument for determining and registering the variations
in the size or volume of a limb, as the arm or leg, and hence
the variations in the amount of blood in the limb.
[1913 Webster] -- {Pleth`ys*mo*graph"ic}, a.
[1913 Webster]