ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 513 



and if the new compound is also coloured, and either not or only slightly 

 diosmotic, a perceptible accumulation of pigment takes place in the cell. 

 The absorption and storing up of the anilin pigments is not connected with 

 the vital activity of the cell. The following are absorbed by the living cell, 

 viz. methyl-blue, methyl-violet, cyanin, Bismarck-brown, fuchsin, saffranin, 

 methyl-orange, tropseolin, methyl-green, iodine-green, Hoffmann's violet, 

 gentian-violet, rosolic acid. No special staining of the cell-nucleus or 

 chromatophores was observed in any case, but a tinging of the protoplasm 

 with all except methyl-blue, and an accumulation in the cell-sap with all 

 except rosolic acid ; the microsomes, granules, and vacuoles were also 

 stained. No absorption appeared to take place of nigrosin, anilin-blue, 

 marine blue, anilin-grey, eosin, or Congo-red. 



In a subsequent communication,* Dr. Pfeffer states that methyl-blue 

 is largely absorbed by the living cell, a definite chemical compound with 

 tannic acid being formed. The pigment subsequently either remains in 

 the cell or passes out into the surrounding water. This exosmose can also 

 be brought about by the action of citric acid. He suggests that these 

 phenomena may illustrate the analogous phenomena exhibited by the food- 

 materials of plants. 



Modification of Weigert's Method of Staining Tissues of the Central 

 Nervous System.f — Dr. N. M. Gray hardens specimens in Mliller's or 

 Erlicki's fluids, and then transfers directly to 70 per cent, spirit, and after- 

 wards to absolute alcohol for several days. They are then soaked for one 

 or two days in a mixture of equal parts of ether and absolute alcohol, and 

 next transferred to a solution of celloidin, and eventually imbedded in 

 celloidin on cork. The pieces, still fastened to the cork in the celloidiu, 

 are immersed in a solution of neutral acetate of copper (a saturated 

 filtered solution of this salt diluted with an equal volume of water), and 

 allowed to remain in an incubator at 30° or 40° C. for one or two days. 

 The specimens become pea-green after the copper treatment, and the 

 celloidin of a blueish-green. They may now be preserved in 80 per cent, 

 spirit indefinitely. After having made sections, which must still be kept 

 clear of water, they are immersed in the haematoxylin solution, the formula 

 for which is as follows: — Haematoxylin (Merck's, in crystals) 1 part, 

 absolute alcohol 10 parts, water 90 parts. Boil twenty minutes, cool and 

 filter, and to each 100 parts add 1 part of a cold saturated solution of 

 lithium carbonate. The time for staining varies; in general, the larger, 

 the sooner the result : for cord sections 2-3 hours are enough ; for brain 

 sections twenty-four hours are required to colour the very fine fibres of 

 the cortex. 



After staining, the sections, now black, are decolorized by immersion 

 in the following fluid : — Borax 2 parts, ferricyanide of potassium 2^ 

 parts, water 100 parts. For cord, half to several hours ; for brain sections 

 longer. 



From this solution, the sections are transferred to water and well 

 washed, then to 80 per cent, spirit, then absolute alcohol, then cleared up in 

 xylol or creosote, and mounted in xylol- or benzole-balsam. 



Modification of Golgi's Method for Staining the Central Nervous 

 System. J — Signer Tal modifies Golgi's method as follows : — The small 

 pieces of the central nervous system previously prepared by Golgi's method 

 (hardening in bichromate of potash, and subsequent treatment with a 1/2 per 



* Ber. Deutsch. Bot. Gesell., iv. (1886) Gen. Versamml., p. xxx. 



t Amer. Mon. Micr. Joum., viii. (1887) pp. 31-2, from Med. News, 1886. 



X Gazz. Ospit., vii. (1886) No. 68. 



