TENDON JERKS; DRY PATHWAYS IN SPINAL CORD 831 



classes: protopathic, epicritie, and deep or muscular. It is important 

 now for ns to consider what becomes of each of these impulses after 

 entering the spinal cord, for there is abnndanl evidence thai they tr. 

 up to the brain by differenl pathways. This evidence is furnished partly 

 by examination of the cord of patients who during life exhibited per- 

 versions of the skin sensations, and partly by producing experimental 

 lesions affecting differenl p;irts of the spinal cord ill animals. Tn the 

 disease syringomyelia, for example, enlargemenl of the central canal 

 of the spinal cord causes rupture of certain of the tracts and a conse- 

 quent disintegration of the skin sensations; that is, the sensations of pain 

 and temperature disappear, whereas those of touch and deep muscular 

 sensation remain. Or, from the experimental side, if we make a lat < 

 hemiseetion of the spinal eord, then after recovery, so far as we can 

 study it in a dumb animal, we shall he able to show that certain sen- 

 s;iti(ins have disappeared, whereas others remain. Tt is evident, how- 

 ever, that we must judcre by objective and not by subjective phenomena 

 in these experiments, and our results are only approximate and very 

 liable to misinterpretation. Importanl contributions to this subject have 

 recently been made, particularly by Holmes 6 and by Pnllier. 9 on sol- 

 diers wounded in the spinal cord. 



Summing up the results obtained by the earlier investigators, Brown- 

 Sequard sumo sixty years ago stated that hemiseetion of the eord on one 

 side produced the following results: (l") paralysis of voluntary motion 

 of the same side: (2) paralysis of vasomotor control on the same side. 

 so that the limb is hotter than oormal ; (3) anesthesia for all kinds of sen- 

 sation, excepl muscular sense on the side opposite to that of the lesion; 

 <4) a condition of heightened skin sensitivity (Called hyperesthesia) on 



the same side as the lesion, with the exception of a narrow strip of skin 



corresponding to the segmenl at which th rd is cut, which is anesthetic. 



These results indicate that in general the skin sensations "f pain, touch. 



ami temperature cross i>\rv to tl ther side shortly after their entry 



into the corcl. but thai the deep muscular sensations remain in la 



pari uncrossed. More recent experimental and clinical investigations 

 do not support Brown-Sequard's conclusions. 



Ransom has recently shown that the afferent toots of the spinal cord 



contain both medullated and nonmedullated uerve fibers, and he be- 

 lieves that the former transmit the epicritic sensations, and the la- 

 the protopathic. !'•> tracing those different kinds of fibers into the 



spinal COrd, he found thai the nonmedullated lie in Lissauer's tract 

 one or two segments and then pas> into the substantia gelatinOSS R 

 landi. which, therefore, appears to be the nucleus for the reception 



the protopathic impulses 



