The paw is inserted into a special water cell which causes a pressure change due to the immersion.  The attached meter reports this pressure change in ml.  This form of detection eliminates changes due to conductivity alterations at repeated insertions as found on comparable units. The measurements are shown on the units LCD readout at a resolution of 0.01 ml for rats and 0.001 ml for mice.  An angled acrylic stand serves to keep the instrument in position for easy viewing. The water cell is attached to an acrylic stand of its own. The fact that there is no “wetting solution” required is a first for this type of unit. The unit also allows for obstruction free viewing of the test subject with free access to the cell.  The meter is powered by a 9V battery (with approximately 50 hours of operation) or by a power adapter.  Both are supplied with the meter.