208 



PRACTICAL HISTOLOGY. 



[XVII. 



endothelial sheath of the nerve-fibre, composed of polygonal 

 squamcs (fig. 189). 



5. Axis-Cylinder. Harden for two or three days a nerve in 

 chromate of potash, tease a piece, and stain it in carmine. Observe 

 the axis-cylinder stained red (fig. 188). Or treat a fine nerve for 

 four days to a week in -^ per cent, chromic acid or -^ per cent, 

 bichromate of potash. On teasing long stretches of 

 isolated nerve axis-cylinders are readily found. 



6. T.S. of a Nerve. Select a rather large nerve, 

 e.g., the human sciatic, and harden about an inch of 

 it in picric acid for forty-eight hours, or in 2 per 

 cent, ammonium bichromate for two weeks. Wash 

 out the bichromate. 

 Complete the harden- 

 ing in alcohol. Sec- 

 tions may be made, and 

 stained with logwood 

 or carmine, but they 

 are very apt to fall to 

 pieces. It is prefer- 

 able, therefore, to stain 

 the hardened tissue 

 "in bulk." Place it 

 in borax carmine for 

 three days, then trans- 

 fer it to acid alcohol, 

 and pass it through 

 absolute alcohol and 

 turpentine, and embed 

 it in paraffin. Cut 

 sections, when the 

 paraffin keeps all the 

 parts in their places. 



Fix a section on a slide with white of egg, remove 

 cylinder; 6. Ran- a }} t] ie paraffin by placing the slide in turpentine, 

 Nucleus, c'hro- clear it up in clove-oil, and mount in balsam. 



(<i.) (L) Observe the connective-tissue sheath 

 epineurium or sheath surrounding the whole 

 nerve, sending processes into the nerve, numerous 

 bundles some large, others smaller orfuniculi of nerve-fibres, each 

 surrounded by a lamellated sheath perineurium which sends fine 

 septa endoneurium into each funiculus. In each bundle the cut 

 ends of the fibres are directed towards the observer (fig. 190). 



The large blood-vessels are in the epineurium, and a few in the 

 endoneurium. 



FIG. 



Fro. 188. Peri- 

 pheral Nerve- 

 Fibre, a. Axis- 



mate of potash 

 and carmine, x 



200. 



Mouse, Ranvier's Crosses and 

 Endothelial Covering. AgN0 3 , 



x 300. 



