404 CHAPTER XXXI. 



717. Other Modifications or Similar Methods. FLECHSIG, Arch, 

 f. Anat. u. Phys., Phys. Abtli., 1889, p. 537 ; Zeit.f. wiss. Mik., vii, 1890, 

 p. 71; Journ. Boy. Mic. Soc., 1890, p. 538 ; BEEGLIA, Zeit., vii, 2, 1890, 

 p. 36 ; Rossi, ibid., vi, 2, 188, 1889, p. 182 ; MEECIEE, ibid., vii, 4, 1891, 

 p. 480; HAUG, ibid., vii, 2, 1890, p. 153; WALSEM, ibid., xi, 2, 1894, 

 p. 236; ROBEETSON, ibid., xiv, 1897, p. 80 (Brit. Med. Journ., 1897, 

 p. 651) ; HILL, Brain, Ixxiii, 1896 ; Phil. Trans., 184u, 1894, p. 399 ; 

 AEONSON, Centralb. med. Wiss., 1890; Ergebnisse der Anat., vi, 1896 

 (1897), p. 22 (differentiates in a watch -glassful of water containing a few 

 drops of a mixture of equal parts of concentrated solution of calcium 

 chloride and water) ; BOEHM u. OPPEL, ibid., p. 23, who use in the same 

 way hypochlorite of sodium ; HAEEIS, Philadelphia Med. Journ., May 

 14th, 1898 (stains sections [of material hardened as for Weigert's stain] for 

 several hours in a 1 per cent, solution of toluidin blue in 1 per cent, borax 

 solution, and differentiates in saturated aqueous solution of tannic acid). 



Other Myelin Stains. 



718. Osmic Acid (EXNEE, Sitzb. fc. Akad. Wiss. Wien, 1881, Ixxxiii, 

 3 Abth., p. 151 ; BEVAN LEWIS, The Human Brain, p. 105). A small 

 portion of brain, not exceeding a cubic centimetre in size, is placed in ten 

 times its volume of 1 per cent, osmic acid, replaced by fresh after two days. 

 In from five to ten days it is imbedded and cut. The sections are treated 

 by caustic ammonia (20 drops to 50 c.c. of water), which clears up the 

 general mass of the brain substance, leaving medullated fibres black, and 

 are examined in glycerin. According to Weigert the method shows very 

 fine fibres indeed. The preparations are not permanent. 



719, MARCHI'S Method (for Degenerate Nerves) (Rivista 

 sperim. di Freniatria e di Med. leg ale, 1887, p. 208 ; Zeit. f. 

 wiss. Mik., ix, 3, 1893, p. 350). Nerves are first hardened 

 for a week in solution of Miiller, and then put for a few 

 days into a mixture of 2 parts solution of Miiller and 1 part 

 1 per cent, osmic acid solution. The treatment with the 

 chrome salt deprives the medullary sheath of normal fibres 

 of the faculty of impregnating with osmium, whilst the 

 (fatty) degeneration products, in diseased sheaths retain that 

 faculty. In consequence the sheaths in normal nerves 

 acquire a yellow coloration, those of degenerated tracts a 

 black one. 



For the study of degenerate nerve-tracts the method of 

 MAECHI has an advantage over that of WEIGERT, in that it 

 gives positive images of the degenerated elements, Weigert's 

 process only giving negative ones. 



