340 CENTRAL NERVOUS SYSTEM. 



are reduced to powder. The burette is then placed upright, 

 and when the material has all settled the fluid is poured off. 

 The material is then carefully washed with distilled water by 

 repeated decantation, and finally poured into a conical glass 

 burette. The water is then poured off, and the material 

 stained with picro- or ammonia- carmine. This, which takes 

 from twelve to fifteen hours, is followed by preservation in a 

 mixture of 1 part spirit and 3 parts glycerin. By this method 

 cells from spinal cord and cerebellum may be obtained with 

 their processes attached down to the fourth division. 



BEVAN LEWIS'S Compression Method for Fresh Tissue (Mon. 

 Mic. Journ., 1876, p. 106 ; Human Brain, p. 146) is as follows : Vertical 

 sections, as thin as possible, are made from a piece of a convolution of 

 brain from which the membranes have been removed. The sections are 

 made by free hand by means of a section-knife flooded with spirit. The 

 sections are got on to a slide and treated with Miiller's solution for a few 

 seconds. A cover is then put on and steadily pressed down so as to flatten 

 out the sections into an almost transparent film. The slide is then rinsed in 

 water and placed for thirty to forty seconds in a bath of methylated spirit. 

 It is then removed, one edge of the cover-glass steadied with the finger, the 

 blade of a penknife inserted under the opposite edge, and the cover gently 

 lifted. The section, which remains adherent either to the slide or to the 

 cover, is washed with water, stained in any way that may be desired, 

 dehydrated, and mounted in balsam. 



For staining the cells of the cortex, Lewis prefers a 1 per cent, solution 

 of anilin-black. 



He prefers to dehydrate by drying under a bell-glass in the presence of 

 concentrated sulphuric acid. Clear with chloroform in preference to clove 

 oil. Lewis finds that this process results in far less rapture and tearing of 

 nerve-cells and processes than would be imagined ; he considers that " the 

 result is. equivalent to the most delicate teasing of tissue, the processes 

 being gradually unravelled from their dense networks, and the structural 

 elements universally displayed to the best advantage." 



v. THANHOFFEB(Ze^./. wise. Mik., iv, 4, 1887, p. 467) describes a similar 

 process. 



680. Neuroglia (GIERKE, Arch.f. mik. Anat., 1885, p. 444). 

 Maceration in the usual media, chromic solutions, iodised 

 serum, &c., but especially in the liquid of Landois ( 505). 

 For sections, harden for six to ten weeks in bichromate of 

 ammonia, first of 1*5 per cent., and gradually raised to 3 per 

 cent. Avoid paraffin for imbedding, and imbed in celloidin 

 or cut without imbedding. Stain with ammonia- carmine, or 

 picro-carminate of soda, or alum-carmine, or Heidcnhain's 

 hii'inuloxyliii. Other details in this valuable paper. 



