XVII.] 



NERVE-FIBRES. 



211 



Leave it in this fluid for three or four days. Wash every trace of the iron salt 

 out of the preparation, and preserve it in alcohol. Place small pieces of the nerve 

 several days in a saturated solution of dinitrosoresorcin in 75 per cent, alcohol. 

 Tease a fragment, dehydrate it with alcohol, clarify with xylol, 

 and mount in balsam (Plainer). This is an excellent method. 



(a.) Ohserve the axis-cylinder stained green. It can be 

 seen with the utmost distinctness passing from one internode 

 to the next one, and across the nodes of Ranvier, which are 

 particularly sharply denned. In the myelin, a network of 

 fibres the neurokeratin network stained green. The axis- 

 cylinder appears as distinct as in fig. 193. 



(ft.) Klihne and Ewald's Method. 1 Harden a nerve for 

 twenty-four hours in absolute alcohol. Boil it in absolute 

 alcohol, and extract it with ether. To remove everything 

 except the network, a teased preparation is digested in pan- 

 creatic juice. 



(c.) Heidenhain's hoematoxylin (p. 70) may be used to 

 stain nerve-fibres. It stains the axis-cylinder and the neuro- 

 keratin network. 



9. Frommann's Lines and Ranvier's Crosses (H). Place 



a fresh nerve in .c-i per cent, silver nitrate for forty-eight Vlf . ,,. 



11 i i t t-ir i A i -T IG. IQ4- rioni- 



hours, and keep it in the dark. Wash it in water, and mann s Lines 

 expose it to light for 2-3 days in equal parts of formic acid, on an Axial 

 water, and glycerine, and preserve it in glycerine. Tease Cylinder, 

 a piece in glycerine. 



(a.) Observe the crosses of Ranvier sharply denned, and on the axis-cylinder 

 well-defined transverse markings, extending for a long 

 distance along the axis-cylinder. Frommann's lines. If 

 an axis-cylinder be dislodged from its fibre, a biconical 

 swelling may be seen (a). It corresponds to that part of the 

 axis-cylinder opposite a node of Ranvier (fig. 194). 



10. Axis-Cylinder (a.) Action of Collodion (H). Tease 

 a fresh sciatic nerve of a frog without adding any fluid. 

 Add a large drop of collodion and apply a cover-glass, or 

 tease a fresh nerve in chloroform. Examine quickly, as the 

 preparation soon spoils. The neurilemma is distinct, the 

 myelin is transparent and finely granular, while the axis- 

 cylinder appears as a dark cylindrical rod often with a 

 curved course in the centre of the fibre, and it may even 

 project beyond the end of the fibre. 



(ft.) Isolated axis-cylinders are readily obtained from the 

 central nervous system after maceration of the white matter 

 of the cord in methyl-mixture (p. 26), or Miiller's fluid or 

 ammonium chromate. 



11. Schwann's Sheath. Macerate a peripheral nerve for 

 several days in ammonium chromate (i : 3000). The myelin 

 is dissolved while the neurilemma and axis-cylinder remain 

 (Schiefferdccl-cr}. 



12.' T.S. Nerve, Osmic Acid (H). Stretch a nerve on a 

 piece of wood, and place it wood and all for two days in 

 .5 per cent, osmic acid, or, better still, in Flemming's 

 mixture for one day. On the second day, add a little more 

 osmic arid to Flemming's mixture, and harden the nerve 

 for another day. It is better to embed the nerve in paraffin 

 and make transverse sections. The section.? are fixed on a slide by a fixative, 

 1 K Mint's Untersuch. , Heidelberg, 1878. 



FIG. i9v Periphe- 

 ral Nerve-Fibre 

 of Frog. a. Lon- 

 gitudinal fibrillne 

 in axis-cylinder ; 

 b. T.S. of nerve- 

 fibre. Osmic acid 

 and Bismarck 

 brown, x 1000. 



