Fig. 35.—Hand Table Microtome
The hand table microtome (Fig. 35) is provided with a clamp, by which it may be attached to the edge of a table or desk. The cutting surface consists of two separated but parallel glass benches. The object is held by a clamp and is raised by a micrometer screw, which, when moved through one division by turning the divided head, raises the specimen 0.01 mm.
The sliding microtome has a track of 250 mm. The object is held by a clamp and its height regulated by hand. The disk regulating the micrometer screw is divided into one hundred parts. When this is turned through one division, the object is raised 0.005 mm. or 5 microns, at the same time a clock-spring in contact with teeth registers by a clicking sound. If the disk is turned through two divisions, there will be two clicks, etc. In this way is regulated the thickness of the sections cut. When the micrometer screw has been turned through the one hundred divisions, it must be unscrewed, the specimen raised, and the steps of the process repeated. The knife is movable and is drawn across the specimen in making sections.
Fig. 36.—Base Sledge Microtome
The base sledge microtome (Fig. 36) has a heavy iron base which supports a sliding-way on which the object-carrier moves. The object-carrier is mounted on a solid mass of metal, and is provided with a clamp for holding the object. The object is raised by turning a knob which, when turned once, raises the specimen one to twenty microns, according to how the feeding mechanism is set.
Sections thicker than twenty microns may be obtained by turning the knob two or more times. The knife is fixed and is supported by two pillars, the base of which may be moved forward or backward in such a manner that the knife can be arranged with an oblique or right-angled cutting surface.
Fig. 37.—Minot Rotary Microtome
The Minot rotary microtome (Fig. 37) has a fixed knife, held in position by two pillars, and a movable object-carrier. The object is firmly secured by a clamp, and it is raised by a micrometer screw. The screw is attached to a wheel having five hundred teeth on its periphery. A pawl is adjusted to the teeth in such a way that, when moved by turning a wheel to which it is attached, specimens varying from one to twenty-five microns in thickness may be cut, according to the way the adjusting disk is set. When the mechanism has been regulated and the object adjusted for cutting, it is only necessary to turn a crank in cutting sections.