516 GOLGI METHODS 



sections are left for ten or fifteen or twenty minutes, according to 

 their thickness. After a quick washing in distilled water they are 

 passed for three to five minutes into 5 per cent, sodium hypo- 

 sulphite and washed once more in distilled water. From this they 

 are transferred successively into 30, 50, and 70 per cent, alcohols, 

 to each of which 1 drop of saturated iodine tincture to every 5 c.c. 

 of alcohol has been added. Sections remain in each alcohol ten 

 to fifteen minutes and are lastly transferred into pure 70 per cent, 

 alcohol. 



At this point the process is ended, and one can proceed to 

 mount the sections in the usual way, or re-transfer them into 

 distilled water, counterstain them lightly with a carmine solution, 

 dehydrate with alcohols of ascending strength up to 95 per cent., 

 pass them through two changes of carbol-xylol and mount them 

 under a thin cover-glass in xylol-colophonium or balsam. If 

 desirable and safe, the celloidin can be removed before definite 

 mounting by passing sections through absolute alcohol, and 

 alcohol-ether if necessary. 



The process is simpler than the rather complicated platinum 

 substitutions of Robertson and Macdonald [Journ. Merit. Sc, 

 xlvii, 1901, p. 327) and is so quickly and easily carried out that 

 many sections can be manipulated at the same time. 



PROCESSES SIMILAR TO GOLGI'S METHODS OR SUITABLE 

 FOR THE SAME PURPOSES 



1045. Ziehen's Gold and Sublimate Method {Neurol. Centrbl., 

 X, 1891, p. 65). Small pieces of fresh tissues are put into a 

 large quantity of a mixture of equal parts of 1 per cent, corrosive 

 sublimate and 1 per cent, gold chloride, and left therein for at 

 least three weeks, preferably for several months up to five, by 

 which time they will have become of a metallic red-brown colour. 

 They are then gummed to a cork or wooden cube and cut without 

 imbedding. Sections are treated either with Lugol's solution 

 diluted with 4 volumes of water, or with diluted tincture of 

 iodine, until duly differentiated, then washed, dehydrated, and 

 mounted in balsam. Both medullated and non-medullated nerve- 

 fibres, as well as nerve-cells and neuroglia cells are stained. 



1046. Krohnthal's Lead Sulphide Impregnation (Neurol. 

 Centrbl, xviii, 1889 ; Ztschr. wiss. Mikr., xvi, 1899, p. 235). 

 Pure formic acid is slowly added to a saturated solution of lead 

 acetate till white crystals of lead formiate are abundantly formed. 

 The mother liquid is filtered off, and the crystals are dissolved to 

 saturation in distilled water. Equal volumes of this saturated 

 solution of lead formiate and 10 jier cent, formalin form the 

 fixing fluid in which pieces of brain or spinal cord are left for five 

 days. Tissues are then directly brought into a mixture of equal 



