114 



MANUAL OF HISTOLOGY. 



6.-. 



stained in a few hours. The external portions, however, will 

 be stained in a few minutes, and they may be removed by care- 

 ful separation with fine needles. To mount, take a glass slide 

 and slip it under the nerve-fibres, while the needle is employed 

 to carry them up on to a dry part of the slide 

 where they can be placed side by side. Then 

 remove the excess of water with bibulous paper, 

 and let the fibres get so dry that they adhere 

 to the slide. Place about them a ring of tis- 

 sue-paper, so that when the cover is adjusted 

 it will not press upon the fibres. Fix the cover 

 at different points with paraffine, then put a 

 drop of glycerine upon one side, and a drop of 

 water upon the other. The union of water and 

 glycerine should be allowed to go on for 

 twenty-four hours in a damp place. The con- 

 strictions and arrow-markings are usually well 

 seen. The nuclei also are occasionally to be 

 found in a niche of the myeline. These bodies, 

 however, are better seen in specimens that have 

 been a short time (fifteen or twenty minutes) 

 in osmic acid, and then in picro-carmine a few 

 hours. It still is a question among histologists 

 whether the arrow-markings are artificial or 

 not ; each of the sections lying between the 

 markings is called the cylindro-conical segment 

 (Hohlcylinder, Kuhnt). (See Fig. 43.) 



Transverse sections of myelinic 'nerves. 

 Certain points are best seen by making trans- 

 verse sections. Prepare the sciatic of a frog or 

 any of the human peripheral nerves by im- 

 mersing a few days in a sherry-colored solution 

 of bichromate of potash, or in Mueller' s fluid, * 

 and then in 90 per cent, of alcohol, until the tis- 

 sue is hard enough to cut. Then it is to be 

 mounted in the microtome with wax and oil of 

 about its own consistence. Sections are to be made with the 

 razor; or it may be mounted in elder-pith in the following 

 way : bore out from the centre of the pith-cylinder a cylindri- 



1 The well-known eye-fluid, of which the composition is : Bichromate of potash, 

 2 to 2 grammes ; sulphate of soda, 1 gramme ; distilled water, 100 grammes. 



FIG. 46. Human 

 myelinic nerve : a, In- 

 terannular segment ; &, 

 Ranvier's node ; c. nu- 

 cleus of the interannu- 

 lar segment surround- 

 ed by granular proto- 

 plasm; rf, Henle's 

 sheath with nucleus. 



