436 NERVOUS SYSTEM SPECIAL METHODS. 



varying from a few hours to ten days or longer in Veratti's mixture, 

 consisting of- 



5 per cent, potassium bichromate . . 30 parts. 

 0-1 per cent, chloroplatinic acid . 30 ,, 



1 per cent, osmic acid . . . 15 to 30 

 From time to time pieces are put in one or other of Golgi's 

 rejuvenating fluids (as described in 888), and thence into -8 to 1 per 

 cent, silver nitrate. Sections are cut and mounted as by Clolgi's 

 bichromate and nitrate of silver method (see 882). 



846. GOLGI'S Arsenious Acid and Silver Nitrate Method (Arch. 

 Ital. BioL, xlix, 1908, p. 272). Small pieces of quite fresh tissues 

 are fixed for three, six, eight or twelve hours in equal parts of 20 per 

 cent, formalin, saturated solution of arsenious acid, and 96 per cent, 

 alcohol. After a quick wash with distilled water, they are passed 

 for some hours (or days) into 1 per cent, silver nitrate, and then 

 treated with a reducing fluid, usually Cajal's hydroquinone 

 mixture (hydroquinone 20 grms., sodium sulphite 5 grms., formalin 

 50 c.c., water 1000 c.c.). Wash quickly, dehydrate, and embed 

 either in celloidin or paraffin. The sections are toned with equal 

 parts of 1 per cent, gold chloride and a mixture consisting of water 

 1000 c.c., with 30 grms. each of sodium hyposulphite and ammonium 

 sulphocyanide, and then rapidly bleached by the following method, 

 due to VERATTI : Wash the toned sections in distilled water and 

 transfer them for one, two or three minutes into potassium per- 

 manganate 0-5 grm., distilled water 1000 c.c., sulphuric acid 1 c.c. ; 

 wash again ; transfer into 1 per cent, oxalic acid until the yellowish 

 colour imparted to the sections by the potassium permanganate 

 has disappeared ; wash thoroughly in repeatedly changed distilled 

 water ; counterstain, dehydrate, and mount as usual. 



847. RAMON Y CAJAL'S Uranium Nitrate and Silver Nitrate Method 



(Trab. Lab. Invest. BioL, Madrid, xii, 1914, p. 127). (1) Small 

 pieces of quite fresh tissues are fixed for ten to fourteen hours in a 

 mixture of neutralised formalin 15 c.c., distilled water 85 c.c., 

 uranium nitrate 1 grm. Instead of uranium nitrate, uranium 

 acetate, as suggested by Del Rio-Hortega, may be sometimes used. 

 Should a very fine reaction be desirable, the following formula may 

 be employed : Uranium nitrate 1 grm., ethyl or methyl alcohol 

 30 c.c., distilled water 80 c.c., neutralised formalin 15 to 20 c.c. 

 (2) After a quick wash in distilled water, pieces are transferred into 

 1 -5 per cent, silver nitrate and kept therein for thirty-six to forty- 

 eight hours at room temperature. If the pieces are only a few and 



