GOLGI-COX 515 



sections which ought to be made either by free hand or by means 

 of a freezing microtome after shght prehminary washing of the 

 pieces with water, and impregnating them with 20 per cent, 

 dextrin for one to three days as suggested by Mann. 



To convert the white mercury impregnation into a black one, 

 Cox suggested treating the sections for an hour or two with 

 5 per cent, sodium carbonate, but 5 to 10 per cent, ammonia is 

 now generally used. They are then thoroughly washed in distilled 

 water, carefully dehydrated, cleared by one of the usual ways, 

 and mounted, without a cover, either in thick xylol balsam or in 

 the original medium suggested by Cox and composed of : 

 Gum sandarac 75 grm., camphor 15, oil of turpentine 30, oil of 

 lavender 22-5, alcohol 75, castor oil 5 to 10 drops. For examination 

 add a drop of castor oil, and cover. 



1044. Methods for rendering Golgi-Cox Preparations more 

 permanent. Various authors (see Sanders, 1898, in lift, to A. B. 

 Lee, Vade-Mecum, 1913 ed., p. 433 ; Bremer, Anat. Rec, iv, 

 1910, p. 263) have proposed washing tissue treated according to 

 Cox's process in many changes of alcohol, and imbedding them in 

 celloidin — this chiefly with the object of overcoming the difficulty 

 of cutting brittle pieces by means of the freezing microtome, and 

 also of rendering preparations more permanent by removing the 

 excess of corrosive sublimate not utilised by the reaction, and which 

 still permeates the tissues. As a matter of fact sections of pieces 

 thus treated are very easily cut and can be transferred from one 

 to another fluid without danger of injuring them. Moreover, they 

 can be counterstained, and the impregnation keeps sufficiently 

 well, particularly if sections are mounted without a cover-glass. 

 But in such preparations, sometimes quickly, sometimes slowly, 

 opaque granules and minute needle-like crystals almost always 

 become developed. 



To avoid this Da Fano proposed (Proc. Physiol. Soc. Journ. 

 Physiol., liv, 1921) to treat sections much in the same way as 

 by the so-called process of toning and fixing Bielschowsky prepara- 

 tions and the like. (See Da Fang, ibid., liii, 1920.) He proceeds 

 thus : Pieces which, by a trial section, have been found well 

 impregnated, are washed for some hours in distilled water and 

 then brought, through many changes of alcohol of ascending 

 strengths, into absolute alcohol, and then imbedded in celloidin 

 in the usual way. The celloidin blocks are hardened in 70 per cent, 

 alcohol, where they can be safely left for many days and weeks. 

 Sections of the desired thickness are collected in 60 per cent, 

 alcohol, transferred into distilled water and here thoroughly 

 washed. They are then treated for five to ten minutes with 5 per 

 cent, ammonia and washed over again in two or three changes of 

 distilled water. At this point toning is carried out by means of a 

 slightly acidified 0-2 per cent, gold chloride solution, in which 



17—2 



