FUNCTIONS OF THE SPINAL COED. 801 



nerves which arise behind the point of injury, with temporary vaso-motor 

 paralysis. The remote effects are secondary descending degeneration in 

 the crossed and direct pyramidal tracts and ascending degeneration in 

 the poslero-internal columns. If the section is made on one lateral half 

 of the spinal cord (hemisection) paralysis of voluntary movement and 

 vaso-motor paralysis occur on the side of the operation in the parts 

 helow, with loss of sensation on the side opposite to the injury nnd 

 increased sensitiveness on the side of operation, with the exception of 

 a limited area of anaesthesia in the part supplied by the sensory nerves 

 destroyed in the operation. There is also the usual ascending and 

 descending degeneration, the former also appearing in the column of 

 (roll on the opposite side. 



If a longitudinal section is made through the posterior fissure of the 

 cord in the median line, little if any loss of motion results (some fibres 

 of the pyramidal tract cross in the anterior commissure), but a consider- 

 able reduction of sensibility. If the posterior white columns are di- 

 vided there is considerable loss of the tactile, temperature, and muscle 

 senses, although the sensation of pain may still be felt ; no loss of motion 

 results. If the antero-lateral columns of white fibres be divided there is 

 a loss of voluntary motion in a corresponding part of the same side of 

 the body. Such a loss of motion, provided the gray matter be not inter- 

 fered with, is temporary, and indicates that the gray matter may take on 

 the function of conduction, ordinarily carried on by the white columns, 

 past the seat of injury. 



The respiratory and vaso-motor fibres also pass through the antero- 

 lateral white columns. If the gray matter and the posterior white 

 columns be divided sensory or tactile impulses no longer reach the 

 brain, showing that sensory impulses travel in these parts. 



These facts would indicate that sensory impulses entering the 

 posterior roots of the spinal nerves pass for a certain distance in the 

 posterior columns and then cross over to the gray matter of the 

 opposite side to ascend to the cerebrum in the lateral column in front of 

 the pyramidal tract, while some may pass into the posterior column and 

 others ascend in the gray matter ; the fibres concerned in the conduc- 

 tion of " muscular sense " apparently do not decussate until the medulla 

 is reached : or they may pass to the cerebellum by the direct cerebellar 

 tract and posterior columns to the restiform body and thence to the 

 cerebellum. 



On the other hand, voluntary motor impulses after having crossed 

 in the pons varolii and medulla oblongata descend in the antero-lateral 

 columns of white fibres (crossed pyramidal tracts) to leave the cord 

 through the. anterior roots of the spinal nerves, after forming communi- 

 cation with the motor cells of the anterior cornua. The direct pyramidal 



51 



