SPINAL CORD AS A PATH OF CONDUCTION. 173 



at the points of contact. This tract begins in the lumbar region, its 

 fibers arising on the same side from tract cells situated in the inter- 

 mediate portions of the gray matter, or, according to Bruce,* in the 

 lower cells of the column of Clarke. This author states also that 

 fibers belonging to this tract in the lower thoracic region may pass 

 over into the tract of Flechsig at higher levels. Many of the fibers in 

 this tract possibly terminate in the cord itself, since the bundle does 

 not increase regularly in size as it passes up the cord. Most of the 

 bundle continues forward, however, along the ventral side of the 

 pons, gradually shifts more to the dorsal side, and at the level of the 

 superior peduncles of the cerebellum turns backward, for the most 

 part, at least, and passes to the cerebellum by way of the superior 

 peduncle (brachium conjunct ivum) and the anterior medullary 

 velum, to end in the vermiform lobe chiefly on the same side, but to 

 some extent on the opposite sidef (Fig. 78). The area of dis- 

 tribution of these fibers lies anterior or headward of those arising 

 in the dorsal cerebellospinal tract (Flechsig). Where this tract 

 separates from the cerebellospinal fasciculus it is stated t that it 

 gives off a number of fibers which enter the restiform body with 

 the cerebellospinal fasciculus to end in the cerebellum. This 

 and other facts indicate that the two tracts constitute a com- 

 mon system. Regarding the physiology of these two tracts 

 there is little experimental and not much clinical evidence. 

 Some observers have cut the cerebellospinal fasciculus in ani- 

 mals, but with no very obvious effect except again a slight 

 degree of ataxia in the movements below the lesion and some 

 loss of muscular tone. This result, together with the fact 

 that the bundle ends in the cerebellum, gives reason for be- 

 lieving that the fibers convey afferent impulses from the muscles. 

 As we shall see, much evidence of various kinds connects the cere- 

 bellum 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 afferent impulses 

 from the muscles and the joints and other so-called deep sen- 

 sory parts, and since the fibers of the cerebellospinal fasciculus 

 end in the cerebellum, and since experimental lesion of them 

 gives no loss of cutaneous sensibility, but some degree of ataxia, 

 it seems justifiable to conclude that these fibers are physiolog- 

 ically muscle-sense fibers. The similar fibers in the posterior 

 funiculi end eventually in the cortex of the cerebrum, and may 

 be supposed, therefore, to mediate our conscious muscular sensa- 



* Bruce, "Quarterly Journal of Exp. Physiology," 3, 391, 1910. 



t For the literature upon these tracts see Van Gehuchten, "Le NeVraxe," 

 3, 157, 1901; Horsley and Macnalty, "Brain," 1909, 237, and Bruce, loc. cit. 



tSchafer and Bruce, "Journal of Physiology," 1907 ("Proc. Physiol. 

 Soc."). 



Bing, "ArchivfUr Physiologic," 1906, 250; also Horsley and Macnalty, 

 loc. cit. 



