SPINAL CORD AS A PATH OF CONDUCTION. 165 



the physiology of ihese two tracts there is little experimental 

 and less clinical evidence. Some observers have cut the tract of 

 Flechsig in animals, but with no very obvious effect except again 

 a slight degree of ataxia in the movements below the lesion. This 

 result together with the fact that the bundle ends in the cerebellum 

 gives reason for believing that the fibers mediate muscular sen- 

 sibility. As we shall see, much evidence of every kind connects 

 the cerebellum with the co-ordination of the muscles of the body 

 in the complex movements of standing and locomotion. This 

 power of co-ordination in turn depends upon the sensory impulses 

 from the muscles, and since the fibers of the tract of 'Flechsig end 

 in the cerebellum, and since experimental lesion of them gives no 

 loss of cutaneous sensibility and some degree of ataxia, it seems 

 justifiable to conclude that these fibers are physiologically muscle- 

 sense fibers. The tract of Gowers has not been the subject of much 

 experimental study from the physiological side. Clinically the tract 

 may be involved in pathological or traumatic lesions of the lateral 

 columns, and Gowers* himself gives a history of some such cases 

 which lead him to believe that this tract constitutes a pathway for 

 pain impulses. Little confidence, however, can be placed in this 

 conclusion, since the lesions in question were not confined to the 

 column of Gowers, but involved neighboring regions and the gray 

 matter. The only positive indication that we have concerning 

 the physiological value of these fibers is given by their histology in 

 the fact that they end in the cerebellum. This fact would connect 

 them with the co-ordination of the muscles in movements of equili- 

 bration, and would therefore make them fibers of muscle sense. 

 It would seem, therefore, that all the long ascending tracts in the 

 posterior and lateral columns of the cord are made up of fibers of 

 muscle sense. The immense importance of muscular sensibility in 

 the maintenance of life and in defense against enemies may explain, 

 upon the doctrine of the struggle for existence, why the long paths 

 should have been developed first in connection with this sense. 



The Spinal Paths for the Cutaneous Senses (Touch, Pain, 

 and Temperature). From the facts stated in the last paragraph 

 it follows that the spinal paths for touch, pain, and temperature 

 must be along the short association tracts of the ground bundles 

 of the lateral and anterior columns. There is evidence from the 

 clinical side that the paths of conduction for these senses are sep- 

 arate. In the pathological condition known as syringomyelia cavi- 

 ties are formed in the cord affecting chiefly the central gray matter 

 and the contiguous portions of the white. In these cases a frequent 

 symptom is what is known as the dissociation of sensations; the 

 patient loses, in certain regions, the sensations of pain and tempera- 

 * Gowers, "Lancet." 1886. 



