676 AN AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



ruption of definite tracts. Unfortunately, however, the material for such a 

 study is very meagre. 



The weight of evidence indicates that the result of a lesion in one lateral 

 half of the spinal cord in man and in the higher animals is followed by a loss 

 or impairment of motion on the same side, and a loss of sensation which is 

 greatest on the side opposite to the lesion. As just cited, there are cases in 

 dogs where the damage caused by the hemisection is apparently transient, 

 and no permanent loss can be demonstrated, but in man the loss of function 

 tends to be, far more persistent. 



On the basis of a case 1 in which the lateral column of the cord and the 

 gray matter of both horns on the same side was the seat of damage, and in 

 which there was a total loss of pain on the opposite side of the body without 

 impairment of tactile sensibility, it may be inferred that the pain-impulses 

 cross soon after entering the cord, and pass cephalad by some path lying within 

 the damaged area. A second case 2 is recorded in which a stab-wound divided 

 all of one-half of the cord plus the dorsal column of the other half. There 

 was here a loss of sensibility to pain on the side opposite the lesion, together 

 with the loss of tactile sensibility on both sides, pointing, therefore, to the 

 dorsal columns as the paths for the tactile impulses. 



The observations of Turner 3 on monkeys, in which hemisection of the cord 

 had been made in the lumbar and thoracic regions indicate that all sensory 

 impulses cross immediately after entering the cord, yet section in the cervical 

 region showed that the impulses roused by touching the skin pass in part on 

 the same side of the cord as the section, the other sensory impulses being, 

 however, completely crossed. 



On the other hand, from his work on hemisection of the dorsal cord of 

 the monkey at different levels, 4 Mott found the disturbance of sensibility of all 

 forms mainly on the side of the section. The evidence for the path of the 

 cutaneous impulses is therefore contradictory. 



In addition to the cutaneous impulses there are the sensory impulses from 

 the viscera, muscles and tendons, which find their path cephalad probably along 

 the direct cerebellar tract as well by the other pathways conducting cephalad. 

 After hemisection of the cord the " muscular " sensations are usually lost on 

 the side of the section. 



Since, then, the dorsal and lateral columns of the cord appear to contain 

 the chief afferent paths for the sensory impulses, the next step in following 

 the pathway is to find the terminations of these tracts. 



The long tracts in the dorsal columns are connected with the nuclei of 

 those columns (nuclei of Goll and of Burdach) on the same side. The cells 

 of these nuclei send their neurons cephalad ; in part they decussate in the 

 sensory crossing and contribute to the formation of the lemniscus, by way of 

 which they pass either directly to the cerebral cortex or reach this only after 



1 Gowers : Clinical Society' 's Transactions, 1878, vol. xi. 



2 Miiller : Seitrdgc zur pathologische Anatomic und Physiologic des Riickcnmarkes, Leipzig, 1871.. 



3 Brain, 1891. * Mott : Journal of Physiology, 1891, vol. xvii. 





