610 



THE FUNCTION OF THE SPINAL CORD 



regarded as at all complete, the material alreadj^ at hand suffices to 

 show that the spinal cord contains definite tracts which in the main 

 correspond with the anatomical grouping previously discussed. The 

 methods employed to trace the course of these different neuron sys- 

 tems are as follows: 1 



(a) Morphological. Different procedures of staining have been made use of 

 in order to differentiate the cell-bodies and their processes more clearly from the 

 surrounding tissue. The impregnation procedures of Weigert and Golgi consist 

 in hardening the preparation in chromate or bichromate and subjecting it subse- 

 quently to a solution of silver nitrate or mercuric chlorid. The silver or mercuric 

 chromate precipitates are not diffuse, but are restricted to certain parts of the 

 neuron and may be bleached sufficiently to allow the tracing of the processes in 



FIG. 302. SCHEMA OF THE TRACTS IN THE SPINAL CORD. (Kolliker.) 

 g, Fasciculus gracilis; b, fasciculus cuneatus; pc, fasciculus cerebrospinalis lateralis; 

 pd, fasciculus cerebrospinalis anterior; /, fasciculus cerebellospinalis; gr, fasciculus 

 anterolateralis superficialis. 



rather thick sections. Ehrlich has advocated the intravitam staining with methy- 

 lene-blue. 



The method of differential staining is frequently employed as a means of 

 recognizing medullated and non-medullated nerve fibers. It has been pointed out 

 by Flechsig that the newly-formed axons are non-medullated, but acquire a sheath 

 when developed sufficiently to become functional. Now, as the different parts of 

 the nervous system attain their full development in a definite sequence, it cannot 

 surprise us to find that the myelination of the various fiber groups takes place 

 successively and at certain intervals from one another. Moreover, as the projec- 

 tion system is the most recent acquisition of the nervous system, we are justified in 

 assuming that the pyramidal tracts, connecting the cerebrum with the cord, re- 



1 Galenus compared the spinal cord to a stream which distributes nervous energy 

 to all parts of the body. Oribasius describes the effects following sections of the 

 cord. These are also discussed in the writings of Hippocrates. 



