320 GOLGI BODIES ETC. 



mixture consisting of water 1000 c.c.. with 30 grm. 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 permanganate 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 permanga- 

 nate has disappeared ; wash thoroughly in repeatedly changed distilled 

 water ; counterstain, dehydrate, and mount as usual. 



723. Ramon y Cajal's Uranium Nitrate and Silver Nitrate 



Method {Trah. 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 some- 

 times 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 small 1 per cent, silver nitrate will be 

 sufficient. (3) Wash quickly and reduce for eight to twenty-four 

 hours in hydroquinone 1 to 2 grm. formalin 15 c.c, distilled water 

 100 c.c, sodium sulphite 0-5 grm. (4) Wash quickly, imbed 

 in paraffin or celloidin, or make sections by the freezing method. 

 (5) Tone and counterstain sections if desirable. Dehydrate and 

 mount as usual. 



Best results are obtained from vertebrates, preferably kittens 

 and young rabbits. The method may be applied to human 

 material, if available in a sufficiently fresh condition. With 

 invertebrates results are not so good, and rather uncertain, so that 

 Cajal advises a simple fixation in formalin or formalin-acetone, 

 followed by impregnation with silver nitrate, as by his reduced 

 silver methods for neurofibrils. 



724. Da Fang's Cobalt Nitrate Modification {Proc. Physiol. 

 Soc. Journ. Physiol., liii, 1920 ; Journ. B. Micr. Soc, 1920, p. 157). 

 Small pieces of quite fresh tissues are fixed for six to eight hours at 

 room temperature in cobalt nitrate 1 grm., distilled water 100 c.c, 

 formalin 15 c.c The solution can be prepared beforehand, and 

 keeps unaltered for months. The formalin need not be neutralised 

 unless strongly acid or containing free sulphuric acid, in which 

 case it is necessary to neutralise it by one of the usual methods. 

 For the fixation of embryonic organs and in all cases in which a 

 shrinkage of delicate tissues is to be feared, the quantity of the 

 formalin may be reduced to 10, 8, or 6 c.c. for every 100 c.c of 

 distilled water. The time of fixation should be shortened to three 

 to four hours or even less in the case of very small pieces, such as 



