ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 313 



or Canada balsam. By this method the fibrillar substance got a distinct 

 blackish staining. 



Mr. Nansen concludes with describing a method the importance of 

 which " for our future knowledge of the nervous system can scarcely be 

 overestimated, as it affords really quite marvellous preparations, and far 

 surpasses every method hitherto known." By modifications of the 

 black chromo-silver method of Prof. Golgi the author has obtained ex- 

 cellent preparations. As employed for Myxine glutinosa the following 

 method is adopted : — The nerve-cord is cut out of the living animal, 

 and divided into pieces one or two centimetres long ; these are laid in a 

 solution of potassium-bichromate (2-2 • 5 per cent.) for about an hour, 

 when the solution is changed and made a little stronger. In this the 

 pieces are left for about twenty-four hours, after which they are put 

 into a fresh solution consisting of 4 parts of 3 per cent, solution of 

 potassium-bichromate and 1 part of 1 per cent, osmic acid, in which 

 they remain for about three days. When the pieces are ready, they are 

 directly treated with silver nitrate; they are first washed in a weak 

 solution (0 • 5 per cent.), and then placed in 1 per cent, solutions. After 

 one day the staining is generally complete. Sections need not be very 

 thin ; if the staining is good the ganglion-cells will be seen with all 

 their processes, and nerve-tubes with their ramifications will appear 

 quite dark or black on a transparent field. 



Specimens intended to be preserved should be washed well in alcohol 

 of 90 to 96 per cent. ; when sufficiently washed they should be placed 

 in absolute alcohol. After some hours of this the sections are placed in 

 pure turpentine, which must be changed several times ; and they are 

 then placed on the slide in dammar-resin dissolved in turpentine. If it 

 is desired to keep the preparation a long time, it must not be protected 

 by a cover-glass ; the dammar is at once dried in a warm bath or incu- 

 bator, when the turpentine is very rapidly evaporated and the dammar 

 becomes quite hard and smooth. The addition of a cover-glass prevents, 

 of course, the evaporation of the turpentine and other volatile oils. 



Prof. Golgi mounts the sections, in dammar, on cover-glasses, and 

 the cover-glasses are again mounted on wooden slides, in the middle of 

 which square apertures are cut to suit the glasses. This excellent 

 method not only admits of the use of oil-immersion lenses, but allows 

 the sections to be examined from both sides, which is often of great im- 

 portance when the sections are thick. Silver-stained preparations should, 

 of course, be kept in the dark when not being used. 



New Method for Investigation of Blood.* — Dr. D. Biocdi describes, 

 a new method for the microscopical examination of the blood. He notes 

 the disadvantages of the methods hitherto practised. Being desirous to 

 study the blood more intimately, by means of sections, he experimented 

 with all sorts of imbedding mixtures without success. Eventually, he 

 fixed the elements by placing drops of fresh blood in 5 c.cm. of 2 per 

 cent, osmic acid solution, and this achieved the first step. The im- 

 bedding was successfully effected, after many attempts, in agar-agar,, 

 so much used by Koch and other bacteriologists. The mixture of blood 

 and osmic acid is placed in dissolved agar at a temperature of 35 -37°„ 

 The fluid is allowed to harden in the usual moulds, is sliced into little 

 portions, placed for some days in 85° alcohol, and cut in pith. The 



* Arch. f. Mikr. Anat., xxxi. (1887) pp. 103-12. 



