CENTRAL NERVOUS SYSTEM. 235 



the side opposite to the hemisection in any case in which this has been strictly 

 confined to the one half of the cord. 1 Sometimes the adjacent posterior 

 column of the other half is injured, and in that event there is impairment of 

 sensation for a time on both sides below the lesion. The motor paralysis, at 

 first complete, becomes gradually incomplete, and finally is difficult or impos- 

 sible to determine. But purely voluntary movements are not recovered or 

 but very imperfectly, although all the ordinary associated movements of the 

 limb are recovered. After about three or four weeks it is difficult to detect 

 any sort of paralysis, but the limb which has been paralyzed is thinner than 

 the other." 



If the hemisection is made above the level of the eighth cervical nerve, 

 the pupil on the same side is relatively contracted and remains so. The 

 dilator fibres and the pilomotor fibres in the cervical sympathetic do not 

 degenerate, but remain excitable. The pupil reacts to light and shade in 

 spite of its being persistently smaller than the other. Excitation of the 

 motor cortex of the opposite cerebral hemisphere produces, as a rule, no move- 

 ments in the limbs which have been paralyzed, even if the associated move- 

 ments have long returned. 



As will be seen from the foregoing paragraphs bearing on the afferent 

 pathways found in the spinal cord of man and the higher mammals, the evi- 

 dence for the path of the cutaneous impulses is decidedly 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 as by the long pathways in the dorsal 

 columns. After hemisection of the cord the "muscular" sensations are 

 usually lost on the side of the section, and the observations of Tschcrmak, 

 already mentioned, point to the long fibres in the dorsal funiculi as the path- 

 way for the impulses from the muscles and joints. 



Indeed, the lack of good evidence for the conduction of any impulses — 

 save those from the muscles and joints — by long tracts in the cord, has led 

 Starr 2 to suggest that the dermal impulses are transmitted by short path- 

 ways through the cord. 



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, whether long or short. 

 Of the latter nothing can be said, 'fhe long tracts in the dorsal columns are 

 connected with the nuclei of those columns (nuclei of Goll and of Burdaeh) 

 on the same side. The cells of these nuclei ^-\u\ their axones 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 about the central gyri, or reach this only after interruption in the 



1 Ferrier and Turner ( Brain, 1891 I describe lose of sensibility in the opposite liind limb in 

 the monkey. Brown-Sequard, as is well known, obtained 1 1 1 i » result in the rahbit. (See also 

 Ferrier, Functions of the Brain, and Orooniam Lectures, 1890.) 



'Starr: Transactions of the American Neurological Association, Twenty-third Meeting, 1897, p. 7. 



