XXX.] SPINAL CORD. 343 



16. Staining the Cord in Bulk in Aniline Blue-Black. Small pieces of the 

 cord are placed iu the following fluid for a day or two : 



Aniline blue-black . . .2 grams. 



Water. . . . 60 cc. 



Alcohol . . . . 40 ,, 



Mount the sections in balsam. 



17. Transverse Markings on Axis-Cylinders and Nerve-Cells. Place small 

 pieces of a perfectly fresh cord in I per cent, silver nitrate solution, and keep 

 them in the dark for forty-eight hours, renewing the fluid several times. 

 Wash the pieces and place them, exposed to light, in the following mixture : 

 Formic acid ( I part), amylic alcohol (i part), and water (100 parts), for 5-7 

 days. Tease a fragment in glycerine and observe the alternate brown and 

 clear markings on the axis-cylinders (Fronimaim's lines) and on the nerve-cells 

 (JaJcimovitch). 1 



18. Isolated Neuroglia-Cells. (a.) These are obtained by the interstitial 

 injection of osmic acid into the white matter of the cord (Lesson XXX. 10.) 

 A small piece is teased and stained with picro-carmine. 



(H) Observe the branched cell, with a granu- 

 lar body and long processes (fig. 321). It re- 

 quires considerable care to dissociate such a 

 cell, and it must usually be looked for and 

 isolated with the aid of a dissecting microscope 

 (p. 22). 



(b.) In sections of the cord prepared by 

 Golgi's method, neuroglia-cells may be stained 

 along with the nerve-cells, and on other occa- 

 sions they may be the only elements on which 

 the silver or mercury takes effect. Note that 

 each cell gives off many very fine processes. F IG> 32I . isolated Neuroglia-Oll 

 Some of the latter may be seen to become of Spinal Cord of Ox. n. Nu- 



(c.) Isolated glia-cells may be found after 



maceration in Landois' fluid (p. 26), and subsequent staining with Magdala- 

 red. 



19. Isolated Nerve-Cells of the Cord. The best dissociating reagents are 

 dilute alcohol or Landois' fluid (3-4 days, p. 26). A staining fluid may be 

 added to the dilute alcohol, and thus dissociation and staining go on simul- 

 taneously. With cells either nerve or glia isolated by Landois' fluid, it is 

 better to stain after maceration. The best stains are Magdala-red, methyl- 

 blue II. (0.5-1 per cent., 5-10, drops added to 10 cc. of the macerating fluid). 

 Lavdowsky' 2 uses a "semidesiccation method" like that used for connective 

 tissue ; the isolated cells are allowed to become nearly dry, and then alcohol 

 is slowly added to remove the remainder of the water (see also Lesson XVIII.). 

 Or after maceration shake the tissue in a very small quantity of water in a test- 

 tube, and place it in a watch-glass, add 6-10 drops of glycerine and a little 

 picro-carmine, and dry the whole over a sulphuric acid desiccator. This 

 removes all the water, and one has then the cells stained in glycerine ready to 

 be mounted. 



20. Pal's Method of Staining Nerve-Fibres. This method requires consider- 

 able care. Harden the cord or brain in Miiller's fluid, makeT.S., and place 

 them in alcohol. Stain iu .75 per cent, watery solution of hnematoxylin con- 



1 Journ. de TAnat. ct de la Phys., xxiv. p. 142, 1888. 



2 Archivf. mik. Anat., xxxviii. p. 264. 



