48 



INTRODUCTION TO NEUROLOGY 



It is possible by a special method of staining devised by Marchi 

 to differentiate myelinated fibers which are in process of degen- 

 eration from the normal fibers with which they may be mingled. 

 This method has often permitted a much more precise deter- 

 mination of the exact course of the fibers of a given peripheral 



Fig. 13. Two motor neurons from the ventral column of gray matter of 

 the spinal cord of a rabbit, taken fifteen days after cutting the sciatic nerve, 

 to illustrate the chromatolysis of the chromophilic substance: A, Cell in 

 which the chromophilic bodies are partially disintegrated (at 6) and the 

 nucleus eccentric; B, cell showing more advanced chromatolysis (c), the 

 chromophilic substance being present only in the dendrites and around the 

 nucleus in the form of a homogeneous mass; a, axon. Compare with these 

 appearances the normal cell of the ventral column shown in Fig. 6. (After 

 Ram6n y Cajal.) 



nerve or central tract than would be possible by the examination 

 of normal material, especially after experimental operations on 

 the lower animals, where the particular collection of fibers under 

 investigation may be severed and then later the animal killed 

 and examined by Marchi's method (see p. 135). 



It is also found that after cutting any group of nerve-fibers the 



