The method of using it is as follows:—Screw the microtome firmly to the table, and with the brass tube supplied with the microtome, punch out a cylinder of carrot to fit into the well. Cut this in half longitudinally, and scrape out enough space in one half of the carrot to take the specimen; then place the other half of carrot in position, and make sure that the specimen is held firmly between them, but it must not be crushed. Now put the cylinder of carrot and specimen into the well of the microtome and commence cutting the section. A good razor will do, but it is better to use the knife which Messrs. Watson supply with the microtome. While cutting keep the knife and plate of the microtome well wetted with dilute methylated spirit, and as sections are cut place them in a saucer of dilute spirit. A number of sections may be cut and preserved in methylated spirit until required for examination or mounting.
When a specimen has a very irregular outline, it cannot be very successfully embedded in carrot; paraffin will then be found to be more suitable. Place the tissue in the well of the microtome in the proper position, pour in enough melted paraffin to cover it, and put it by to get cold and hard before attempting to cut sections.
Fig. 234.—The Cambridge Rocking Microtome.
Cambridge Rocking Microtome.—This new pattern Cambridge Rocking Microtome ([Fig. 234]) possesses advantages over other instruments in use for cutting flat sections, and not parts of a cylindrical surface. The tube containing the paraffin is 30 millimetres in internal diameter instead of 20 millimetres, as in the earlier forms. The forward movement is also increased, so that an object 12 millimetres long can be cut throughout its whole length. It is provided with a dividing arc for reading off the thickness of the section in thousandths of a millimetre. The razor may be fixed either with its edge at right angles to the direction of motion of the object, or diagonally, for giving a slicing cut. The object can also be raised and fixed in position clear of the razor.
This microtome has both steadiness and stiffness in its geometrical arrangement and bearings, while the simplicity and efficiency of its mechanism for advancing the section between each stroke of the razor is remarkable. Although it may appear more complicated at first sight, it is found not to be so when brought into use.
Fig. 235.—Cathcart’s Microtome.
Fig. 235a.—Section Cutting Holder for Microtome.