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TEXT-BOOK OF PHYSIOLOGY 



clearly defined and as well known as is desirable, and only for a few 

 sensations can it be said that their pathways have been determined. The 

 reason for this obscurity lies partly in the difficulties of experimentation, 

 partly in the difficulties of interpretation. Clinical observations are for 

 special reasons more or less untrustworthy. 



Some light is thrown on the location of the afferent pathways by the 

 results that follow a transverse section of one lateral half of the cord in 

 the monkey, or a lesion involving the one lateral half in man. Such a 

 procedure abolishes many if not all forms of cutaneous sensibility on the 

 opposite side below the injury. This would seem to prove that the nerve 

 impulses cross the median plane of the cord immediately or very shortly 

 after entering and then ascend the corresponding half of the cord on 

 their way to the thalamus. At the same time, muscle sensibility is abol- 



... 7 , , , Musclese7isa.tion, 

 light touch Joint sensation 

 -Ligktprcssuro 



FIG. 230. A SCHEMATIC ARRANGEMENT OF THE NERVES MEDIATING EPICRITIC, PROTOPATHIC 

 AND DEEP SENSIBILITY AND THEIR RELATION TO THE SPINAL CORD. 



ished on the same side below the injury. This would seem to prove that 

 the fibers coming from the muscles by way of the dorsal roots, ascend 

 the cord on the same side and in the dorsal funiculus as far as the clavate 

 and cuneate nuclei. It is, however, believed by some investigators that 

 some of the fibers which subserve light touch do not decussate at once, 

 but ascend in the tract of Goll as far as the medulla oblongata, where 

 they, in common with the fibers coming from the muscles, arborize around 

 the nerve-cells in the clavate and cuneate nuclei. 



The results on both sides of the body, which follow a transverse lesion, 

 experimental or traumatic, of one-half of the spinal cord in the thoracic 

 region for example, are shown in the subjoined table, a grouping of results 

 which is known as the Brown-Se*quard "Symptom Complex." It is under- 

 stood, of course, that these results are observed below the level of the 

 lesion. 



