THE SPINAL CORD 559 



THE BROWN-SEQUARD SYMPTOM COMPLEX 



Side Opposite of Lesion. Side of Lesion. 



1. Temperature sensibilities abolished, i. Temperature sensibilities re- 



tained. 



2. Painful sensibilities abolished. 2. Painful sensibility retained. 



3. Pressure (painful) sensibilities abol- 3. Pressure (painful) sensibilities 

 ished. retained. 



4. Passive position of limb and direc- 4. Passive position of limb and di- 

 tion of movement, retained. rection of movement, abolished. 



5. Light pressure or light touch, may or 5. Light pressure or light touch, 

 may not be abolished. retained. 



6. Tactile discrimination, retained. 6. Tactile discrimination, abol- 



ished. 



7. Cutaneous localization, abolished. 7. Cutaneous localization, retained. 



8. Voluntary motion, retained. 8. Voluntary motion, abolished. 



From a study of this table it is apparent: (i) that some forms of sensor 

 impulses (those of pain and temperature sensibility) cross soon after their 

 entrance and pass up the opposite side of the cord; (2) that other forms of 

 sensor impulses (those of the sense of passive position of a limb and of the 

 direction of movement and tactile discrimination (Head)) do not cross, but 

 pass up on the same side as the entering dorsal nerve roots; (3) that tactile 

 sensibility may or may not be abolished on the side opposite the lesion; and 

 (4) that the sense of cutaneous localization and tactile discrimination 

 may be dissociated from the sense of passive position, and remain intact 

 when the latter is absent (Head) . 



Descending or Encephalo-spinal Conduction. The conduction of 

 nerve impulses* from above downward necessitates the existence of tracts 

 of nerve-fibers which extend from the encephalon to various levels of 

 the spinal cord. The most important of these tracts is : 



The Cortico-spinal or the Pyramidal Tract. This tract associates the 

 motor area of the cortex with efferent nerve-cells in the ventral gray 

 matter of the aqueduct of Sylvius, of the pons, the medulla oblongata 

 and of the spinal cord. The efferent cells give origin to nerve-fibers 

 which collectively constitute the encephalic and spinal nerves, all of which 

 are distributed to skeletal muscles. 



The reason for the development of this pathway is apparent from the 

 following considerations: 



At birth the child is capable of performing all the functions of organic 

 life, such as sucking, swallowing, breathing, etc. It is, however, deficient 

 in psychic activity and in volitional control of its muscles. Its movements 

 are therefore largely, if not entirely, reflex in character. 



Embryologic and histologic examination of the spinal cord and medulla 

 show that so far as their mechanisms for independent physiologic activities 

 are concerned both are fully developed. Similar investigations of the cere- 

 bral hemispheres and of the nerve-fibers which bring their nerve-cells into 

 relation with the spinal segments show that the cells of the cortex are not only 

 immature, but that their descending axons are incompletely invested with 

 myelin. With the growth of the child, psychic life unfolds and volitional 



