410 ril/M'TO XXXIII. 



material is to be hardened in bichromate and imbedded in 

 celloidin (see last ). It is then (according to the latest form 

 of the process, Eucycl. mik. Technik., 1903 ; p. 942 ; for the 

 earlier form see last ed.) put for 24 hours in a stove into a 

 solution of 2-J- parts of fluoride of chromium, 5 of acetate of 

 copper, and 5 of acetic acid in 100 of water.* 



Sections are then made and stained for from four to 

 twenty-four hours at the temperature of the room in a 

 freshly prepared mixture of 9 vols. of (A) a mixture of 

 7 c.c. of saturated aqueous solution of carbonate of lithium 

 with 93 c.c. of water, and 1 vol. of (B) a solution of I grin, of 

 hsematoxylin in 10 c.c. of alcohol (A and B may be kept in 

 stock, but A must not be too old). The sections should be 

 loose ones, and not thicker than 0'025 mm. They are then 

 washed in several changes of water, and treated with 90 per 

 cent, alcohol, followed by carbolic-acid-and-xylol mixture 

 (for a short time only), or by a mixture of 2 parts of anilin 

 oil with 1 of xylol, then pure xylol and xylol balsam (not 

 chloroform balsam). 



It was, however, found that preparations thus made, 

 without differential ion, did not keep well, and WKKIKKT 

 (Ergebnifte d. Anat., iii, 1894, p. 21) reverted to the practice 

 of differentiating with the borax-ferricyanide mixture,, last ^. 



Later still (Encycl mik. Teclnik., 1903, p. 942) he 

 employed a stain composed of equal parts of (A) a mixture 

 of 4 c.c. of the officinal Liquor ferri scsquichlcrati with 96 of 

 water, and (B) a mixture of 10 c.c. of 10 per cent, solution 

 of hcernatoxylin in alcohol with 90 of 96 per cent, alcohol. 

 The two must be mixed immediately before use, and the 

 sections should remain in the stain over night or longer, then 

 be rinsed and differentiated as usual. This has the advantage 

 of demonstrating very fine fibres, and of giving a caltmrlc^ 

 ground. 



For difficult objects the differentiating liquid may be 

 diluted with water, and gives better results than dilule 

 acetic or hydrochloric acid or the like, which were formerly 

 recommended. 



Formol material may (Ergelni&se, vi, 1897, p. 14) be 



* Instead of the chromium fluoride, you may take rhr< m' alum, us 

 Weigert did at one time, and us some still do. But then you must Imfl, 

 as directed for Weigert's Neuroglia stain, 838. 



