The following is not the outcome of a systematic investigation of the technique of the method of WEIGERT, but simply of experiments made at various times to secure the best results on material hardened as described below. Notes were often made which have been collated and the conclusions presented, not so much as invariable improvements on the regular procedure, but as suggestions for securing better results in certain cases. In the estimation of the success of a WEIGERT preparation, especial weight has been attached to the number of fibers revealed in the gray and the brilliancy with which they are demonstrated. The material consisted of portions of the central nervous system, especially the cord, of the human foetus, infant and adult. This material was fixed in formalin, in potassium bichromate and formalin, or in copper bichromate. The fixation in formalin was usually accomplished by injecting into the blood vessels formalin 1 vol. water several volumes. After removal the brain and cord were kept in formalin 1 vol. + water 9 vols. until used. Some material which yielded fine preparations had been thus kept in formalin for three years. The material fixed in potassium bichromate and formalin was usually fixed by an injection in situ of potassium bichromate 5%, or stronger, several vols. + formalin 1 vol. After removal, the cord and portions of brain were further hardened in potas. sium bichromate 5% 9 vols. + formalin 1 vol. about a week and in potassium bichromate 5% alone for ten days to 2 weeks or Finally, some material, the brain and cord of a 7 months SO. foetus, was fixed by injection in situ of copper bichromate 5% I vol. + formalin 1 vol and further hardened, after removal, in copper bichromate 3% 9 vols. + formalin I vol. for about a week. A method pursued with some selachian material for the study of the cranial nerves will be described below. In order to give an idea of the various combinations of mordanting and decolorizing tried upon the above material a condensed list is given below together with the general character of the results. The staining fluid used was either WEIGERT'S alkaline haematoxylin (abbreviated in the list to "A. h.") or a neutral haematoxylin solution composed of 1 vol. of 10% solution of haematoxylin in absolute alcohol + 9 vols. of water ("N. h."). Where the kind of haematoxylin solution used is uncertain the abbreviation is "H." The word "osmic" indicates that the section was placed in osmic acid. When this was done after the removal from the haematoxylin the section was simply rinsed in water, placed in 4% solution of osmic acid for 4 to 1 minute and then rinsed again in water, previously to decolorization. A. Celloidin sections of material (principally cord of infant and of eight months foetus) fixed and hardened in potassium bichro 2. Copper acetate. A. h., H. and N. h. Osmïc. Pal. sults often good, in some cases fine preparations. 3. Copper acetate. 4. Copper acetate. 5. Copper acetate. Re Osmic. A. h. Osmic. Pal. Fine results. results-distinctly inferior to the Pal. 6. Copper acetate. H. Osmic. Borax-ferricyanide. what better than 5. Some 7. Copper bichromate. A. h. and N. h. Borax-ferricyanide. Not good. 8. Copper bichromate. H. Pal. Good. 9. Copper bichromate. H. Osmic. Pal. Very good. This 10. 17. • 18. 19. 20. Potassium bichromate. A. h. and N. h. Pal. Not good. Fair. Potassium bichromate. Iron alum. H. Osmic. Pal. Good. 22. 23. 24. Failure. Not good. Borax-ferri B. C. Blocks of tissue, hardened like A, imbedded in celloidin, mordanted in toto in copper bichromate several days. The sections made were then treated as follows: 1. A. h. (at higher temperature part of time) Osmic. Pal. 2. A. h. (at higher temperature part of time.) Pal. Not very 3. A. h. (at higher temperature part of time.) Borax-ferricyanide. Failure. Cord of a seven months foetus hardened in copper bichromate formalin as above described. The celloidin sections made were treated as follows: I. 2. Calcium bichromate (5%, 13 days). A. h. Osmic. Pal. Fine. 3. Copper acetate. H. Osmic. Pal. Good. preparations were in many cases practically as good as those that were re-mordanted, there being only a slight diminution in the intensity of the stain. D. Cerebrum of infant. Hardened in formalin as described above. Imbedded in celloidin without mordanting. E. I. 2. were treated as follows: Sections made Copper acetate 46 hours. A. h. 11⁄2 hours. Osmic. Pal. Not good, fibers very pale. Copper acetate 46 hours. A. h. 11⁄2 hours. Borax-ferricyanide. Not good. 3. Copper bichromate 46 hours. A. h. 11⁄2 hours. Osmic. Pal. Not good. Somewhat better than 1. 4. Copper bichromate 46 hours. A. h. 11⁄2 hours. Boraxferricyanide. Not good. 5. Copper bichromate 46 hours. A. h 11⁄2 hours. Osmic. Borax-ferricyanide. Not good. 6. Copper bichromate 46 hours. A. h. 47 hours. Osmic. Pal. Better than any of preceding. 7. Copper bichromate 46 hours. Pal. Like 6. 8. Copper bichromate 46 hours ferricyanide. Not good. A. h. 23 hours. Osmic. A. h. 23 hours. Borax Even the best of the above were too pale, perhaps partly, but hardly principally, attributable to the youth of the brain. Cord and medulla of infant 12 months old. Hardened in formalin as above described. Pieces mordanted in toto, immediately after removal from formalin, in copper bichromate 3% for seven or eight days. Imbedded in STEPANOW'S clove oil celloidin.1 I. 2. Sections were treated as follows: No further mordant. A. h. 12 hours. Osmic. Pal. Good. good. 3. Copper bichromate 4 hours. Osmic. Pal. Very N. h. 15 hours. Osmic. Pal. Very fine, better than 1 and 2. 4. Copper bichromate 18 hours. N. h. and A. h. 6 hours. Osmic. Pal. Slightly inferior to 3. 1 Zeitschrift für wiss. Mikroskopie, Bd. XVII, H 2, 1900. |