XXX.] SPINAL CORD. 34! 



Formerly Weigert used acid-fuchsin for staining the medullated 

 nerve-fibres of the central nervous system, but this method is now 

 given up in favour of the haematoxylin copper method. 



7. Neuroglia (H). Stain in safranin (24 hours) thin sections of 

 the white matter of the cord hardened in M tiller's fluid, partially 

 decolorise in absolute alcohol, and mount in balsam. 



(a.) Observe the branching neuroglia-cells between the white 

 nerve-fibres (fig. 316, c). The connective-tissue elements have a 

 tint more towards the violet, and are thus differentiated from the 

 nervous elements. The network of neuroglia-fibres is readily seen 

 near the surface of the cord. 



8. Blood- Vessels of the Spinal Cord. Mount a transverse sec- 

 tion of the cord, with its blood-vessels injected. Cut the cord in 

 paraffin. The sections must be rather thick (L and H). Inject the 

 animal, e.g., cat or rabbit, from the aorta with a blue or red mass. 

 Harden in alcohol. 



(a.) Observe the greater vascularity of the grey matter as com- 

 pared with the white. A blood-vessel may be seen running into the 

 anterior median fissure, and at the bottom of it dividing, and giving 

 a branch to each mass of grey matter. 



(b.) The dense plexus of capillaries in the grey matter. Branches 

 of blood-vessels passing into the cord along the roots of the nerves 

 and along the larger septa, which pass from the pia mater into the 

 cord. 



9. Nerve-Fibres of the Spinal Cord (H). Crush a piece of the 

 white matter of the cord, either fresh, or after maceration in ^ per 

 cent, bichromate of potash, between a cover-glass and a slide. 



(a.) Observe the nerve-fibres, many of them with lateral bulgings, 

 or presenting a beaded or moniliform appearance. This is due to 

 the fact that these nerve-fibres are devoid of a primitive sheath. 



(6.) Droplets of "myelin" with concentric markings are seen in 

 the field. 



10. Nerve-Fibres of the Spinal Cord (H). By means of a 

 hypodermic syringe make an interstitial injection of I per cent, 

 osmic acid into the white matter of the antero-lateral column of the 

 spinal cord of an ox. Tease a piece in glycerine. 



(a.) Observe tubes of different sizes, many varicose, with incisures 

 and cylinder- cones, but no primitive sheath 



11. Staining the Cord. To stain sections the following dyes 

 may be used : 



(i.) Ordinary carmine, picro-carmine, or acid-carmine. In using 

 the last, use a very dilute (scarcely coloured) solution, and let the 

 sections remain in the solution for 1-2 weeks. (2.) These stains 

 may be combined with hsematoxylin. (3.) Benzo-azurin. (4.) 

 Aniline-blue soluble in water but insoluble in spirit. (5.) The same 



