Abstract: A microtome, in particular an ultramicrotome, having a specimen carrier which can be moved relative to a knife. The specimen carrier includes a clamping aperture for holding a specimen. A light source is located inside the clamping aperture in the specimen carrier so that light is transmitted, from the rear of the clamping aperture, through a specimen block which is composed of a transparent material and through the specimen.

Abstract: A cooling apparatus utilizing liquid nitrogen for cooling specimens to temperatures in the range from -100.degree. C. to -195.degree. C. in propane, halogenated hydrocarbons, isopentane, or other cooling media. Freezing of the cooling media is avoided by means of an arrangement wherein the liquid nitrogen cools the cooling-bath container and/or the liquifier only initially, but after the desired cooling-bath temperature has been reached, the liquid nitrogen level is lowered to below the height of a protective shell which results in further cooling being only indirect, via solid/solid contacts and via the gas phase. A constant cooling-bath temperature is ensured by means of a thermostatic temperature-control system while trouble-free standby operation is ensured by means of an automatic system for replenishing liquid nitrogen, and by a system for controlling the level of liquid nitrogen. Safe disposal of the cooling media which may be combustible and/or toxic is provided for.

Abstract: A microtome, especially an ultramicrotome, is disclosed in which a forward-feed system for the specimen arm and/or knife of the microtome comprises a stepping motor which is controlled by a pulse generator and which shifts the specimen arm, and the knife, relative to each other by an appropriate amount of forward feed in accordance with a forward-feed value which is set at one of a plurality of preselector switches. In order to facilitate quick switching over from one forward-feed amplitude to another, permitting the selection of forward-feed amplitudes which differ by an order of magnitude, for example, if semi-thin sections are to be produced during a run of ultra-thin sections, the forward-feed amplitudes set by the preselector switches can be switched, according to choice, to the pulse generator for the stepping motor by means of a changeover switch. This arrangement enables the operator to alter the forward-feed amplitude by one manual action without disturbing the ongoing operation.