840 SUMMARY OF CURRENT RESEARCHES RELATING TO 



examined were removed from the living or jast-killed animal, and were 

 placed in the preserving fluid in very small pieces. 



Preparing Cochlea of Guinea-pig-.* — Dr. G. Schwalbe places the fresh 

 cochlea of the guinea-pig for eight to ten hours in Flemming's solution, 

 and after thorough washing, decalcifies in one per cent, hydrochloric acid 

 wherein it requires to remain for twenty-four hours. After the acid is 

 quite washed out, absolute alcohol, xylol, xylol paraffin, saturation with 

 Spec's paraffin at 35°-60^ C. If the animal killed with the chloroform is 

 allowed to hang with the head downwards for some hours, a perfectly 

 natural injection of the cochlear vessels is obtained. To isolate these 

 Vissels, the following maceration method is recommended : — The cochlea 

 filled with blood is decalcified in three per cent, hydrochloric acid and is 

 then kept at a temperature of 40° in an incubator in the same acid. In one 

 or two days the sheath of the cochlea is so softened that the nervous 

 cochlea and its spiral expansion can be isolated from the basilar membrane, 

 and the ductus cochlearis unwound from the expansion of the nerve. After 

 separating the nerve and the duct the spiral vein can be seen with a low 

 power lying by the ganglion spirale and beneath this the tractus spiralis 

 glomerulorum winding round the nervus cochle8B, 



Preparing the Central Nervous System of Acephala.t — For the ex- 

 amination of the central nervous system of mussels. Dr. B. Eawitz recom- 

 mends (1) absolute alcohol 1 part to 3 parts distilled water. This keeps 

 the parts perfectly and causes a slight isolation of the cells, and yet 

 affords useful pictures after four to five weeks. With Solbrig's one-sixth 

 spirit, the contents of the nerve-fibrils disappeared, and Eanvier's one-third 

 spirit could only be used for one day as decomposition appearances occurred 

 afterwards. (2) Bichromate of potash in solutions of 0*2, 0'05, 0'025 

 per cent, effected perfect maceration in 8 to 24 hours ; after a longer period 

 the tissues became completely softened. For hardening the animal in the 

 shell a 5 per cent, solution was used for 4 to 6 weeks. The animals 

 were then easily separated from the shell. After 8 days in absolute alcohol 

 the ganglia were sectioned. (3) Bichromate of ammonia in • 1 per cent, 

 solution caused shrinking of the nuclei, and changes in the central nervous 

 system. (4) Chromic acid is said to be as useless as a maceration medium 

 as it is for hardening ; even Arnold's chromacetic acid solution produced 

 changes in the tissues. (5) Haller's fluid quite destroyed the nervous 

 elements of the Acephala in half an hour. (6) Osmic acid was of very 

 little use. Solutions of O'l and 0*05 per cent, were inferior to spirit or 

 bichromate of potash ; with solutions of 1 and 2 per cent, the cells seemed 

 to be scorched. 5 to 10 drops of a cold saturated solution of picric acid to 

 15 cc. of distilled water effected the isolation of cells in 12 to 24 hours and 

 gave good pictures. The mixture of spirit and iodine used by Fritsch for 

 the brains of fish and followed by bichromate were found to make the 

 nervous system very brittle. 



As stains, rubin, safranin and eosin gave the best pictures. Gentian- 

 violet, malachite-green, and Weigert's heematoxylin were useless. Ammo- 

 niacal carmine and much diluted solutions of " Eosenliqueurs " stain 

 excellently, especially the central nervous network. The objects remain 

 therein 4-10 days ; they are then washed in spirit slightly acidulated with 

 acetic acid, then absolute alcohol. Gold chloride in • 1 to • 25 per cent, 

 solutions gives good pictures. 



* ' Beitrage zur Physiologie. Carl Ludwig zu seinem 70. Geburtstage gewidmet von 

 Beinera Schiilcrn,' 1887. Cf. Zcitschr. f. Wiss. Mikr., iv. (1887) p. 90. 



t Jeuaische Zcitachr. f. Natunviss., xx. (1887) pp. 38-1-460 (5 pis.). Ct supra, p, 735. 



