THE SPINAL CORD. 



395 



Destructive lesions in certain parts 

 by descending secondary degenerations, 

 through the crura cerebri, the anterior 

 pyramids, and the posterior parts of the 

 lateral columns of the cord, that is through 

 the entire length of the pyramidal tracts. 

 Such a condition causes paralysis of volun- 

 tary movement, without diminishing the 

 power of sensibility. If the degeneration be 

 confined to one lateral half of the spinal 

 cord, paralysis exists only on that side ; if it 

 be bilateral both sides of the body are para- 

 lyzed. Similar descending degenerations 

 may take place from any point where a 

 lesion exists in the pyramidal tracts, and 

 according to Charcot* these tracts may 

 also be affected by a primary alteration 

 throughout their extent in the medulla ob- 

 longata and spinal. cord. 



As the pyramidal tracts, in descending 

 through the medulla oblongata, reach the 

 decussation of the pyramids, a portion of 

 their fibres is continued upon the same 

 side of the median line, forming a narrow 

 band on the inner border of the anterior 

 column. These bands are the Columns of 

 (Fig. 106, Section I.). They rapidly 

 diminish in size from above downward, 

 and in man come to a termination in the 

 lower part of the cervical region. The 

 greater part of the pyramidal tract c 

 the median line at the decussation of the 

 pyramids to the opposite side, and is thence 

 traceable quite to the lower extremity of 

 the cord. In the cervical region it occupies 

 most of the lateral column, but in the 

 dorsal region is confined to its posterior 

 half, and in the lumbar region is still further 

 reduced. Its fibres no doubt leave it at 

 successive points from above downward, 

 to enter the gray substance of the anterior 

 horn. 



The preceding facts are derived from 

 pathological anatomy. But similar results 



of the brain are followed 



TRANSVERSE SECTIONS OF THE 

 SPIXAL CORD; showing degener- 

 ation of the Pyramidal Tracts; 

 from a patient with bilateral 

 paralysis. (Charcot.) I. Upper 

 part of Cervical Enlargement. II. 

 Lower Cervical Region. ILL Dor- 

 sal Region. IV. Lumbar En- 

 largement. The degenerated por- 

 tions are shaded in transverse 

 lines. In Section I., the Columns 

 of Turck are visible at the inner 

 edge of the anterior columns. 



* Lemons sur les Maladies du Systeme Nerveux. Paris, 1877. tome ii., p. 219. 



