50G SUMMARY OF CURRENT RESEARCHES RELATING TO 



and unswollen. In Phycochromacea) tho nucleus was demonstrated in 

 Tolypothrix, JEijagrojnla, and Oscillarla sp. ; it was best shown by 

 digesting the fresh filament, then extracting with ether-alcohol and 

 examining in a 0-3 per cent, salt solution. The author also treats of 

 the resting and active condition of the nuclous, and the cells taking part 

 in reproduction. 



Preparation of Nerve-cells and Peripheral Ganglia.* — Anna Kot- 

 larewsky employed in her researches on tho spinal ganglia, and on tho 

 Gasserian ganglion four different hardening methods. (1) Hardening 

 in acids : 3 per cent, nitric acid ; half per cent, chromic acid ; 1 per- 

 cent, osmic acid ; 1 per cent, picric acid, and Flemming's mixture. 

 The preparations were imbedded in celloidin, or paraffin. Next to 

 freshly examined cells, tho picric acid was found to produce the best 

 effect. Flemming's mixture had an unfavourable action on the shape of 

 tho cells. In all tho preparations hardened in acids, the outline of tho 

 cells was sharp ; the cell-body took stains well, but the nucleus only 

 slightly, though the nucleoli were well coloured. (2) Hardening in 

 acid salts (Muller's solution). (3) Hardening in neutral media (neutral 

 acetate of lead and spirit) : Cells in the preparations treated with 10 per 

 cent, solution of acetate of lead showed excellent fixation ; hardening in 

 spirit was less favourable. (4) Hardening in alkaline media : Basic 

 acetate of lead and ammoniacal chloride of silver (1 per cent.) were used. 

 Both solutions penetrated only slowly, so that the superficial layers 

 could be used. The depth to which the hardening medium had pene- 

 trated was determined by treating the sections with hydric sulphide or 

 bichromate of potash. 



The hardened objects were variously stained. (1) With metals : 

 Osmic acid used for preparations hardened in Muller's fluid effected no 

 remarkable differentiation of the nervous elements. After-treatment 

 with ammoniacal silver solution (reduction being effected in an incu- 

 bator) gave a better result. In this way good pictures were obtained 

 in 24 hours ; the preparations, however, did not keep. (2) With nuclear 

 stains : these affected the bodies of the nerve-cells more than the nuclei, 

 the corpuscles in the latter behaving in a way similar to the cell-body. 

 Gentian-violet and hematoxylin stained the granula of the body of the 

 cell ; carmine in neutral solution did not. Merkel's staining method gave 

 favourable results for differentiating the chromopbilous and chromo- 

 phobous cells. (3) Dyes were used which do not stain the nucleus; 

 eosin, fuchsin, nigrosin. Of these, nigrosin produced in the lead pre- 

 parations interesting pictures, the dye having stained the protoplasm, 

 a reticulated appearance was imparted to the cell-body. In the lead 

 preparations, eosin stained the nucleus pretty dark, and the cell-body of 

 the nerve-cells diffusely. Methylen-blue was examined by dissolving it 

 in • 7 per cent, salt solution, and injecting it into the spinal lymph-sac 

 or abdominal cavity of a frog. Some time after the injection the ganglia 

 were removed as quickly as possible, and examined in salt solution or 

 glycerin. The cells were stained in about one or two hours. 



Methsemogiobin Crystals.f — According to Dr. W. D. Halliburton 

 the following is an easy way to obtain these crystals : — 



Defibrinate a few cubic centimetres of the blood of a rat, guinea-pig, 



* MT. Naturf. Gesoll. Bern, 1887, pp. 3-23. 



t St. Louis Med. and Surg. Journ., liv. (188S) p. 96. 



