182 



THE TISSUES. 



Dendrite. 



axis-cylinders sometimes appear as round dots and again as stellate figures. 

 The latter are due to pressure on the shrinking axial cord by the unevenly 

 coagulated medullary sheath. As the medullary sheath in such prepara- 

 tions crumbles away in many places, large areas of the axis- cylinder may 

 often be isolated by teasing (Fig. 149). 



Sensory and motor nerve- endings may be stained after gold chlorid 

 and chrome-silver methods (see methods of impregnation, page 47), or 

 after the infra vitam methylene-blue method suggested by Ehrlich and 

 variously modified by other investigators. 



If freshly teased fibers be treated with glacial acetic acid, the 

 axis-cylinders swell up and issue from the ends of the fibers in irregular 

 masses showing fine longitudinal striation (Kolliker, 93). The structures 

 of the axial space dissolve in i% hydrochloric acid, as well as in a 10% 

 solution of sodium chlorid (Halliburton). 



For the isolation of ganglion cells, 33% alcohol, o.i to 0.5% 

 chromic acid, or i^ solution of potassium bichromate may be used. 



Small pieces of the spinal 

 cord and brain containing 

 ganglion cells are treated 

 with a small quantity of 

 one of the above solutions 

 for one or two weeks. After 

 this interval the prepara- 

 tions may be teased and 

 the isolated ganglion cells 

 stained on a slide and 

 mounted in glycerin. They 

 may even be fixed in situ 

 by injecting a i % solution 

 of osmic acid or 33% al- 

 cohol into the areas of 

 the brain or spinal cord 

 containing ganglion cells. 

 The region thus treated is 

 then cut out and teased. 



The nonmedullated or 

 "Remak's fibers" are ob- 

 tained by teasing a sym- 

 pathetic nerve, or, better, 

 a piece of the vagus pre- 

 viously treated with osmic 

 acid. Between the black- 

 ened medullated fibers of 

 the pneumogastric are seen numerous unstained fibers of Remak. 



The fibers of the olfactory nerve are stained brown by osmic acid. 



Ehrlich' s methylene-blue method consists in an intra vitam 

 staining of ganglion cells, nerve-fibers, and nerve-endings. The method 

 is much more applicable to the staining of peripheral ganglia (spinal and 

 sympathetic ganglia), peripheral nerves, and nerve-endings than to stain- 

 ing the elements of the central nervous system, although the latter may 

 also be stained by means of this method. 



Two methods for bringing the stain in contact with the nerve -tissues 

 are now in use : (i) injecting the methylene-blue solution into the living 



Neuraxis. 



Fig. 150. A ganglion cell from anterior horn 

 of the spinal cord of calf ; teased preparation ; 

 X I4O. By this method only the coarsest ramifica- 

 tions of the dendrites are preserved ; the rest are 

 torn off. 



