402 CENTRAL NEEVOUS SYSTEM. 



766. The methylen blue impregnation method has been 

 described in Chap. IX, and its great importance has been 

 insisted on. 



767. The Gold Method is one of the most important methods 

 for the study of the finer nerve-fibrils of the spinal cord. 

 The instructions given by GERLACH (Strieker's Handb., p. 

 678) have been already quoted, ante, 228, p. 148. 



BOLL (Arch. f. Psych, u. Nervenk., iv, p. 42 ; GIERKE, Zeit. 

 f. wiss. Mik., 1884, p. 403) makes the following observations 

 on Gerlach's process : The hardening in bichromate ought 

 not to be prolonged further than is absolutely necessary, for 

 after eight days the elective susceptibility of the tissues for 

 gold impregnation begins to diminish, and after fifteen days 

 has almost disappeared. The knife should not be wetted 

 with alcohol ; the tissues should never be allowed to come 

 into contact with alcohol. Only a small quantity of gold 

 solution, relatively to the volume of the sections, should be 

 taken. The impregnation should last for twelve hours. 



Gierke (1. c.) says, " Gerlach's gold preparations have never 

 had their equal for the demonstration of very fine nerve- 

 fibrils. Weigert's Saurefuchsin preparations are the only 

 ones that can be compared with them in this respect." 



SCHIEFFERDECKER (Arch, f. mik. Anat.j 1874, p. 472) also 

 recommends gold chloride for demonstrating fine networks in 

 transverse sections. Strength 1 : 5000 or 10,000. Time about 

 one to three hours. After washing in water the sections are 

 put for twenty-four hours into acetic acid of f to 1 per cent., 

 then mounted in balsam. 



According to the same author, chloride of palladium may 

 advantageously be used for the demonstration of the longitu- 

 dinal fibres, and (of course, therefore) for staining longitudinal 

 sections. A solution of 1 : 10,000 strength is taken ; the sec- 

 tions remain in it till light brown (about three to five hours). 

 For somef urther methods of the same author see I.e., 1878,p. 38. 



MERKEL'S chloride of palladium and carmine method has 

 been given above, 746. 



768. FREUD'S gold method (Arch. f. Anat. u. Phys., 1884, 

 p. 453) may be used for controlling the results obtained by 

 Weigert's process, and for obtaining an impregnation of axis- 



