174 



LECTURES ON THE CENTRAL NERVOUS SYSTEM. 



I will mention only a few points which are either particu- 

 larly important or have been established beyond a doubt: 



Diseases of the pyramidal tract in the lateral, and apparently in the anterior 

 columns as well, cause paresis or paralysis. In addition to this, the weakened or 

 paralyzed muscles are in a condition of increased tension, have a tendency to con- 

 tracture, and are abnormally responsive to mechanical irritants. Wherever you 

 see these symptoms, either alone or mixed with others, you may with all safety 

 assume that the pyramidal tract is involved in the disease. 



irnrlnde, 



FIG. 103. 

 Diagram of innervation of a muscle. 



.Vnt. A T Ti'., Motor nerve. M>ixkrl, Muscle. 



Vorderhvrnzflli; Ant. -root cell. VorAef-Wnrsel, Ant. root. 

 llirnriiulr, Cortex of the brain. 



43 



FIG. 104. 



Localization of a lesion in the anterior 

 horn of the gray matter in the lumbar en- 

 largement, taken from a two-year-old child 

 eleven months after the commencement of 

 the disease. A large lesion in the right and a 

 smaller one in the left anterior horn. Sec- 

 tions made 13. 23,30, 36, and 43 mm. above the 

 liluuu terminate. (From Erb, after Roth. 



Diseases of the posterior columns give rise to symptoms varying according 

 to the area of the columns involved. Injuries to the posterior roots at their 

 entrance break up the continuity of the sensory tract which runs in the latter, and 

 cause a loss, not only of every kind of sensation, but also of the reflexes which 

 are set in motion by the sensory tract. The reflexes which have no direct con- 

 nection with conscious sensation, as the tendon reflexes, also disappear. Degen- 

 erations of the posterior columns, which do not injure the entering posterior 

 roots, or only slightly affect them, may not give rise to any serious disturbance of 

 cutaneous sensation, but the muscle-sense invariably appears to suffer. The main 



