t 



1894.] MICROSCOPICAL JOURNAL 343 



these two muscles, we see between them the nerve, which 

 we isolate down to the knee joint, on a level with which 

 it bifurcates. Take every precaution to touch the nerve 

 as little as possible, and especially avoid seizing it with 

 the forceps. A blunt probe will serve to raise it. The 

 nerve must be fixed in a state of physiological extension. 

 Ranvier's process being classic it is well to repeat that 

 learned histologist's experience point by point. Take a 

 little stem of wood, a match for instance,. . . .slip it un- 

 der the nerve and fasten the latter by two ligatures, tak- 

 ing care to put one b6low the bifurcation. Cut the nerve 

 beyond the ligatures and put it in 1 per cent osmic acid. 

 . . . .As beginners often stretch the nerve too much, the 

 following modification may be used. The nerve being 

 well isolated, with a pipette filled with 1 per cent osmic 

 acid, wet it while it is still in place. A few drops are 

 enough if the pipette be passed along the length of the 

 nerve. In 3 or 4 minutes it may be cut and will not con- 

 tract ; put it in the osmium solution for ^ an hour, wash 

 in a large quantity of water. It is in this bath that we 

 begin the dissociation. Sieze each bifurcating fascicle 

 with fine forceps, and tear gently. The nerve being di- 

 vided into two fascicles, repeat the operation upon each 

 until a fascicle is obtained containing only a few nerve 

 tubes. Place on a slide, examine with a low power, and 

 if suflBciently dissociated, add a drop of alum carmine 

 which is to be replaced by glycerine when the nuclei are 

 stained. 



Fibres without myeline, or Remack's fibres, exist in 

 considerable number in the pneumogastric nerve. This 

 may be had from the dog, the rabbit, man, etc., but as it 

 is easy to be found in the frog we select that animal. . . . 

 A frog, immobilised by piercing the spinal chord, is put 

 on its back, the sternum cut in the median line and the 

 two parts of the thoracic walls are separated so as to ex- 

 pose the pericardium and the lungs ; introduce a strong 



