6. 80 per cent alcohol 1-3 hours.
7. Cut.
The quick celloidin methods recommended in the literature (Kaufmann, Stepanow, Scholz and others) require more time, and do not give better results. Material received from operative clinics late in the afternoon can be sectioned and stained usually by ten o’clock the next morning.
2. PARAFFIN IMBEDDING. A paraffin of a melting-point sufficiently high enough to withstand summer heat is advisable; a 52°C. paraffin answers for this latitude. The use of softer paraffins is not necessary. The paraffin-oven should be regulated at a constant temperature of 54-55°C. Over-heating of the tissue while in the oven must be carefully safeguarded, so that in the management of a paraffin-oven the care of the thermo-regulator is the most important thing.
Slow Paraffin Method.
1. Thorough dehydration in absolute alcohol 12-24 hours.
2. Aniline oil to remove alcohol, until tissue becomes transparent or sinks.
3. 1st. Xylol, ½ hour, to remove aniline oil.
4. 2nd. Xylol, 1-2 hours, until translucent.
5. 1st. Paraffin, 52°C. in oven, 1 hour, to remove xylol.
6. 2nd. Paraffin, 52°C. in oven, 1-12 hours.
7. Block.
The use of xylol-paraffin is not necessary. For blocking staining dishes, watch-glasses, glass salt-cellars, paper-boxes, metal frames., etc., may be used. A thin smear of tincture of green soap or glycerin is rubbed over the inside of the imbedding box, and it is nearly filled with fresh melted paraffin. With warm forceps the tissue is taken out of the bottle of second paraffin in the oven, and arranged in the melted paraffin in the imbedding dish in the proper position for cutting. Care must be taken that the melted paraffin is not hot enough to “burn” the tissue, else its staining-power may be affected. The surface of the paraffin is then cooled by blowing upon it, and as soon as a film appears upon the surface, the dish is carefully immersed in cold water, so that the paraffin may set quickly. When cool the paraffin-block should slip out of the dish and float to the surface. It is then trimmed to the desired shape, leaving a good matrix of paraffin around the tissue. The paraffin-block is then fastened to a wooden block or to the object-holder of the microtome by means of melted paraffin (a hot knife is drawn along the under-surface of the block and the latter immediately pressed upon the wooden block or object-holder). Chloroform, cedar oil, benzene, carbon bisulphide, etc., may be used instead of xylol, and each one possesses certain advantages for certain purposes. Benzene is advisable for osmic-acid preparations.
Rapid Paraffin Method.
The above method can be greatly shortened for uterine curettings, thin bits of tissue, etc., if the various steps are closely watched, and if the entire process is carried on in the oven. The whole process may be carried out in 1-3 hours, a very great advantage over the quick celloidin method. A simpler and cheaper method is that recommended by Heller, Henke and Brunk, as follows:—
Acetone Method.