PAL'S METHOD. 365 



Modifications of Weigert's Method. 



689. MAX FLESCH (Zeit.f. wiss. Mik., 1884, p. 564). Sec- 

 tions, made either by the celloidin process or otherwise, are 

 put for a few minutes or longer into O5 per cent, chromic 

 acid solution; they are then rinsed in water, and brought 

 into the stain, where they take on a sufficient coloration" 

 much more rapidly than the tissues will if stained in the 

 mass. Decoloration is done in the usual way. No stove is 

 required in this process, and either brown .or green material 

 may be used. Flesch finds (1. c., 1886, p. 51) that this method 

 is to be preferred to Weigert's copper method in all cases in 

 which it is important to produce differential staining in nerve- 

 cells, and especially in the study of peripheral ganglia, and 

 also for producing differential staining of the medulla of 

 central and peripheral nerves, whilst the copper process is 

 most certainly superior for the demonstration of fine nerve- 

 fibres. 



690. BENDA (Verhandl. Physiol Ges. Berlin, 1885-6, Nos. 12, 13, 14 ; 

 Zeit. f. wiss. Mik., iii, 3, 1886, p. 410 ; Arch. f. Anat. u. Phys., 1886, p. 

 562). The tissues are to be fixed and hardened for at least three days in 

 saturated solution of picric acid, washed out for several days in water, 

 hardened in alcohol, imbedded in paraffin, and sections made. (The treat- 

 ment with water after picric acid seems to me to be most inimical to the 

 good preservation of the tissues, and I cannot understand why Benda should 

 not have used alcohol.) The sections are mordanted by treating them for a 

 few minutes or hours with a salt of iron, for which purpose concentrated 

 solution of ammonio-sulphate of iron is recommended. After being well 

 washed in several changes of water, they are stained for about ten minutes 

 in 1 per cent, aqueous solution of haematoxylin, then decoloured by treatment 

 for about five minutes in O'Oo per cent, aqueous solution of chromic acid, 

 rinsed in water, dehydrated, cleared, and mounted in balsam. 



This method is stated to be peculiarly adapted for the demonstration of 

 very fine fibres and their relations to ganglion-cells. 



691. HAMILTON (Journ. of Anat. and Physiol., xxi, 1887, p. 444; Journ. 

 Roy. Mic. Soc., 1888, p. 1051) mordants his preparations with a copper sul- 

 phate solution, and makes sections by the freezing method, after imbedding 

 in collodion. 



BEEVOE (Brain, 1885, p. 227 ; Journ. Roy. Mic. Soc., 1886, p. 898) gives 

 a very slight modification of Weigert's original process. 



692. PAL (Wien. med. Jahrb., 1886; Zeit.f. wiss. Mik., iv, 

 1, 1887, p. 92; Med. Jahrb., 1887^p. 589; Zeit. f. wiss. Mik., 

 1888, p. 88) describes the following process : After staining 



