The instrument provides samples of uniform and reproducible thickness, minimizes damage to surfaces of slices and thereby eliminates the main sources of error in tissue slice work. Slices from approximately 100 to 500 microns in thickness can be prepared at a maximum rate of one slice every 3 to 4 seconds. The slicer operates submerged in a buffer selected by the operator as most appropriate in terms of composition, tonicity, pH, temperature, oxygenation and lubricating properties to maintain the viability of the tissues being sectioned. The microtome and the reservoir with the glass trap are sterilizable to allow the preparation of aseptic slices suitable for prolonged organ culture. The actual slicing is done by a rapidly reciprocating disposable blade oscillating at 1000 to 2500 rpm driven by a motor that also powers the impeller. The tissue slicer contains a cooling block which allows the temperature of the buffer solution in the slicer’s reservoir to be maintained.