THE VERTEBRAL COLUMN. 



487 



FUNCTIONS OF THE CORD AND SPINAL LOCALIZATION. 



The direct or anterior pyramidal tract is motor; the impulse coming from the 

 cerebral cortex passes down the spinal cord on the same side and thence to the ante- 

 rior horn of the opposite side to supply mainly the muscles of the arm and trunk. 

 The crossed or lateral pyramidal tract transmits motor impulses coming from the 

 cortex which cross in the lower part of the medulla and descend on the opposite side. 

 It supplies muscles on the same side as that on which the tract is. The direct cere- 

 bellar tract conveys impressions of equilibrium. The anterolateral tract (ascending 

 tract of Gowers) conveys impressions of temperature and pain. The vestibulospinal 

 tract (descending tract of Lowenthal) is an indirect motor path. 



Lissaiier ' s tract is composed of ascending fibres from the posterior nerve-roots. 

 The posterolateral (column of Burdach) conveys common sensation. The postero- 

 median (column of Goll) conveys muscular sense. 



POSTE 

 LATERA 

 ARTEI 



FIG. 489. Diagram of the spinal cord in the lower cervical region, with its blood-vessels. 



Pyramidal Tract, Motor paralysis below, spastic condition of paralyzed area; 

 exaggerated reflexes ; contractures ; degeneration downward. 



Posterior Columns. Sensory disturbances ; ataxia ; sensation of temperature 

 and pain diminished ; reflexes abolished ; upward degeneration of postero-internal 

 column. 



Anterior Horn. Motor paralysis ; muscle atrophy ; reflexes abolished ; degen- 

 eration descends and muscles show reaction of degeneration. 



Posterior Horn. Sensory disturbances or anaesthesia, such as follows lesion of 

 posterior column. 



Anterior Root. Same as anterior horn. 



Posterior Root. Anaesthesia, if complete ; hyperalgesia and pain if irritative. 



Central Canal. Painful and sensory impressions not properly recognized, while 

 tactile or contact impressions are unaffected ; joint dystrophies. 



One Lateral Half . Brown-Sequard syndrome ; complete loss of power below on 

 the same side as lesion and slight loss of power below on opposite side ; anaesthesia 

 complete on opposite side below lesion. 



LESIONS OF THE CORD. 



The lesions affecting principally the gray matter of the cord are anterior polio- 

 myelitis, syringomyelia, progressive muscular atrophy, and arthritic muscular atrophy. 



Anterior Poliomyelitis. In anterior poliomyelitis or infantile paralysis the 

 lesion is mainly in the anterior horn and is evidenced by a paralysis of the muscles 



