342 PRACTICAL HISTOLOGY. [xxx. 



blue with eosin or Magdala-red. If (5) be used the axis-cylinders 

 are blue, the myelin rose, and there is also a sharp distinction in 

 colour between the nerve-cells and glia-cells. (6.) AVatery solution 

 of Congo-red. The sections are dipped for a moment into very 

 dilute sulphuric or hydrochloric acid (i drop to 10 cc. water). 

 They become blue. (7.) Weigert's hamiatoxylin-copper. (8.) 

 Golgi's silver and mercuric-chloride method. The M tiller's fluid 

 should contain 33.5 grams of potassic bichromate to i gram of 

 sodic sulphate. (9.) Golgi's silver method and sections stained by 

 Magdala- red (Lavdowsky). 



12. Tracts in the Spinal Cord. These are made out histo- 

 logically by studying (a.) embryonic cords in mammals from the 5th 

 to the Qth month. These sections are stained either by Weigert's 

 method (p. 338) or by the modified Pal method. A T.S. of the 

 cord of a human foetus just before birth shows the nerve-fibres in 

 the pyramidal tracts still devoid of myelin, and thus they are easily 

 mapped out from the other parts of the cord which are already 

 medullated. 



(b.) The degeneration changes resulting after hemi-section or 

 section of the cord. Section of the cord is practised say 6-10 days 

 before the cord is required. Parts of the cord above and below the 

 seat of injury are hardened for 10 days or so in Miiller's fluid. 

 Thin pieces are then placed for several days in Marchi's fluid 



(P- 347)- 



Sections are mounted in balsam. All the nerve-fibres which 

 have undergone degeneration are stained black ; healthy .nerve- 

 fibres are yellowish (p. 347). Or instead, Weigert's process may be 

 used, as then the degenerated tracts remain unstained owing to the 

 absence of myelin. 



ADDITIONAL EXERCISES. 



13. Dry Preparation. Stain a T.S. with metliylene-blue (i per cent). 

 Wash it, and allow it to dry on a slide. Add a drop of balsam. This shows 

 very well the general characters of the cord ; the multipolar nerve-cells arc 

 somewhat shrunken, but still they and their processes are well stained. 



14. Sections in Ehrlich-Biondi's Fluid. Place sections in tins fluid (p. 81) 

 well diluted (i : 40), and heat them in a watch-glass until vapour is just given 

 off. Mount thern in balsam, clarifying either with xylol or aniline-oil and 

 xylol (Lesson III. 16). The glia-fibrils are violet in tint, and so is the con- 

 nective tissue generally ; the nuclei of the glia-cells bluish, the myelin orange, 

 the axis-cylinder somewhat violet The cells in the grey matter have a 

 pleasant violet tint. Benzo-azurin can be used in the same way. 



15. T.S. Cord. Eosin and Logwood. The neuroglia-cells, connective- 

 tissue, and epithelium of the central canal have a logwood tint, the other parts 

 are rosy. 



