THE COURSE OF THE FIBERS IN THE SPINAL CORD. 



361 



motor tracts in combination. Of these the best obseryed is the amyotrophic 

 lateral sclerosis. Here the clinical signs — paresis, spasms, muscular atrophy 

 — correspond to the anatomic condition: disease of the pyramidal tracts 

 and of the ventral horn-cells. 



These relations are readily understood by a glance at the preceding 

 schematic representation (Fig. 229). A lesion, located in the line xac {i.e., 

 in the fibers it represents), produces paralysis. If it interrupt this line above 



Uimrlnde, 



Fig. 229. — Schema of innervation of a muscle. Hirnrinde, Brain-cortex. Torder- 

 hormelle, Cell of ant. horn. Tordervmrzel, Anterior root. 



the ganglion-cell, as at x or a, it assumes the character of a central paralysis, 

 without atrophy, and eventuates often in improvement or cure, probably 

 through the substitution of other paths for those represented by x a. If, 

 however, the line a; a c be broken at the ganglion-cell or anywhere in c, then 

 there follows not only paralysis, but also wasting of the paralyzed nerves, and 

 atrophy of their corresponding muscles. As a consequence, the outlook 

 toVard recovery in the paralyzed members is very slight. At times after a 



