854 NEUROLOGY 





The fibers of tactile discrimination, according to Head and Thompson, pass up in 

 the fasciculus cuneatus and fasciculus gracilis of the same side and follow the pa~h 

 of the muscle-sense fibers. The axons of the second order arising in the nucleus 

 cuneatus and gracilis cross with the internal arcuate fibers and ascend tothethalamus 

 with the medial lemniscus, thence by neurons of higher order the impulses are carried 

 to the somatic sensory area of the cortex through the internal capsule. The other 

 touch fibers, shortly after entering the spinal cord, terminate in the dorsal column 

 or intermediate gray matter. Neurons of the second order send their axons through 

 the anterior commissure to pass upward in the antero-lateral funiculus probably 

 in the ventral spinothalamic fasciculus. In the medulla they join or pass upward 

 in the neighborhood of the medial lemniscus to the thalamus and thence by neurons 

 of higher order to the somatic sensory area of the cortex. 



The remaining ascending fasciculi form a part of the complex known as the super- 

 ficial antero-lateral fasciculus (tract of Gowers). The spinotectal fasciculus, as its 

 name indicates, is supposed to have its origin in the gray matter of the cord and 

 terminations in the superior and inferior (?) colliculi of the mid-brain serving for 

 reflexes between the cord and the visceral and auditory centers of the mid-brain. 



The spino-olivary fasciculus (olivospinal; bidbospinal, Helweg's bundle) is likewise 

 of unknown constitution and function; there is uncertainty even in regard to the 

 direction of its fibers. 



Sympathetic afferent fibers (visceral afferent; viscera-sensory; splanchnic afferent) 

 enter the spinal cord by the posterior roots of the thoracic and first two or three 

 lumbar nerves and the second to the fourth sacral nerves. The fibers pass to these 

 nerves from the peripheral sympathetic system through the white rami communi- 

 cantes. Some of the cell bodies of these afferent fibers are located in the spinal 

 ganglia and others are in the sympathetic ganglia. Some of the afferent sympa- 

 thetic fibers end about the cell bodies of somatic sensory neurons and visceral 

 impulses are thus transmitted to these neurons which conduct them as well as their 

 own special impulses to the spinal cord. Other sympathetic afferent neurons 

 whose cell bodies are located in the spinal ganglia send collaterals to neighboring 

 cells of somatic sensory neurons and thus have a double path of transmission to 

 the spinal cord. Such an arrangement provides a mechanism for some of the 

 referred pains. 



These sympathetic afferent fibers presumably divide on entering the spinal cord 

 into ascending and descending branches. Their distribution and termination 

 within the spinal cord are unknown. Some of them probably eventually come into 

 relation with the sympathetic efferent fibers whose cell bodies are located in the 

 lateral column. Our knowledge concerning both the termination and origin of 

 these fibers is very unsatisfactory. 



The sympathetic efferent fibers (splanchnic motor; viscera-motor; preganglionic fibers) 

 are supposed to arise from cells in the intermediate zone between the dorsal 

 and ventral gray columns and in the intermedio-lateral column at the margin of 

 the lateral column. These preganglionic sympathetic fibers are not distributed 

 throughout the entire series of spinal nerves but are confined to two groups, the 

 thoraco-lumbar from the first thoracic to the second or third lumbar nerves and 

 the sacral group from the second to the fourth sacral nerves. They pass out with 

 the anterior root fibers and through the rami communicantes to end in sympathetic 

 ganglia. The impulses are distributed from cells in these ganglia through post- 

 ganglionic fibers to the smooth muscles and glands. The thoraco-lumbar outflow 

 and the sacral outflow form two distinct functional groups which are considered 

 more fully under the sympathetic system. 



