710 SUMMARY OF CURRENT RESEARCHES RELATING TO 



si urn, then washed in water, and transferred to the staining mixture, 

 [nstead of bichromate of potassium, the following mixturo may bo 

 used with equal suecess, but with somewhat different results :— Water, 

 100 ccm. ; alum, 1 grm. ; bichromate of potassium, 1 grin. 



Weigert's Improved Method for the Central Nervous System.*— 

 Trof. C. Wcigcrt's method has been adopted everywhere with great 

 rapidity, as it offers advantages exceeding those of other methods. 

 One of its imperfections (which has been obviated by Prof. Flesch) 

 is that it is only applicable to preparations which have becomo 

 browned by the action of chrome salts. Another is that it docs not 

 stain so many fibres (in tho cerebral cortex for example) as can bo 

 shown by Exner's osmium method. Prof. Weigert has accordingly 

 made some further improvements which obviate this objection. Tho 

 new process is as follows : — 



1. The pieces fastened to a cork with celloidin are immersed in a 

 solution of copper oxide (a saturated filtered solution of this salt 

 diluted with an equal volume of water) and allowed to remain in an 

 incubator for two days. It does not matter if the pieces are still 

 brown or have become green, so long as they were once brown. More- 

 over, if they have lain in alcohol for some time, a surface precipitate 

 is not so easily thrown down. After the copper treatment the pieces 

 become green, the celloidin blueish green. They may now be 

 preserved in 80 per cent, alcohol. 



2. For staining tho sections tho hematoxylin solution is now 

 modified by adding a slight quantity of some alkali ; it is a matter 

 of indifference which ; this addition gives it a brownish violet tone. 

 The proportion of a saturated alkaline solution is ono to one hundred 

 of the logwood solution. In this solution the sections are placed, 

 and owing to the action of the copper no incubator is needed. For 

 cord sections two hours suffice; brain preparations require an immersion 

 of twenty-four hours, in order that the fine cortical fibres may be 

 stained. The staining solution can only be used once. 



For differentiation the borax and prussiate solutions must bo 

 diluted with an equal volume of water. 



Skatol and Carbazol, two new Reagents for Woody Fibre, f — 

 Dr. O. Mattirolo proposes skatol and carbazol as substitutes for 

 phloroglucin and indol as tests for wood fibre. Both of these bodies 

 give identical reactions, i. e. they impart a violet red colour to 

 ligneous tissue. Carbazol is doubly recommended, as it is found in 

 commerce, and is almost altogether without odour ; while 6katol is 

 so offensively malodorous that this property of itself is almost 

 sufficient to bar its use in micro-chemistry. Carbazol, one of tho 

 products of crude anthracene, boiling between 320° and 360°, is pro- 

 duced in the manufacture of anilin from coal. Skatol is obtained 

 from human feces or by synthesis in the dry distillation of nitro- 

 cuminate of barium. 



The author has demonstrated microscopically that skatol and 



* Fortschr. d. Med., iii. (1885) p. 236. Cf. Zeitschr. f. Wiss. Mikr., ii. (1885) 

 pp. 399-401. t Zeitschr. f. Wiws. Mikr., ii. (1885) pp. 354-5. 



