Fig. 225.—Stricker’s Warm Stage.
Stricker’s Stage ([Fig. 225]) consists of a rectangular box with a central opening, C, permitting the passage of light through the specimen under examination. The water makes its exit and entrance at the side tubes B B′, and the temperature is indicated by a thermometer in front. In this apparatus either warm or cold water can be continuously used.
Fig. 226.—Schäfer’s Warm Stage.
Schäfer’s apparatus ([Fig. 226]) consists of a vessel filled with water (seen near the stage) which has been first boiled to expel the air, and then heated by means of a gas flame. The warm water ascends the india-rubber tubing to the brass box on the stage. The box is pierced by a tubular aperture to admit light to the object, and has an exit tube by which the cooled water from the stage returns by another piece of tubing to be reheated by the gas flame. There is a gas-regulator, by means of which any temperature can be maintained.
Methods of Preparing, Hardening, Staining and Section Cutting.
Numerous methods are employed for the preparation, hardening, staining, and section cutting of animal and vegetable tissues for the microscope, the details of which are modified, or varied as may be found needful, from time to time, by those whose intimate acquaintance with the subject entitles them to make innovations and changes in this very important department of microscopy. In the hands of the original worker, formulæ and methods will only be regarded as finger-posts pointing out a means of saving time in turning over pages to find this or that special method of staining. For this particular reason I have collected all the most accredited formulæ together in an Appendix at the end of the book, and arranged them alphabetically for ready reference.
As to section cutting, the student will do well to practise himself in making dissections, thick and thin sections, of vegetable and animal substances. The medical student will require no advice on this point, as the use of the scalpel, and those instruments needed for microscopical work, form an important part of his education. Of all the instruments contrived for delicate dissections, none are more serviceable than those which the student may make for himself out of ordinary needles. These may be fixed in handles as represented in [Fig. 229], in addition to which, a pair of scissors and forceps, and a few small knives, such as those used in eye-operations, will prove most suitable. The double-bladed scissors represented in [Fig. 227], with curved blades, are brought into use for cutting vegetable and other soft structures, the disadvantage attendant upon the use of which is owing to the curvature of the blades; when dealing with flat surfaces, the middle of the section is left too thick to exhibit structure.
The double-bladed knife of Professor Valentin was formerly held in high estimation by the microscopist, but this has been almost superseded by the microtome, which has taken the place of all other instruments, since by its aid uniform series of nearly all substances can be cut. The standard unit of a perfect section cutter, of any kind, has been fixed by the Royal Microscopical Society at the one-thousandth of a millimetre.
