172 



PHYSIOLOGY OF CENTRAL NERVOUS SYSTEM. 



cross in the cord and pass upward in the anterior funiculi. To 

 summarize, therefore, we may say that the evidence at hand 

 proves that the ascending fibers of the posterior funiculi do not 

 convey impulses of pain or temperature, that if they convey 

 any cutaneous touch (pressure) impulses, they certainly do not 

 form the only path of conduction for this sense, and that most 

 probably their chief function is the conduction of impulses of muscle 

 sense, that is, they consist of those deep sensory fibers from the 

 voluntary muscles, the tendons, and the joints, through which we 

 obtain an idea of the position of the limbs and the state of con- 

 traction of the muscles. The sensations thus aroused in the higher 

 parts of the brain are necessary to the proper co-ordination of the 

 movements of the muscles. Injury to these funiculi, therefore, 

 while it does not cause paralysis, is followed by disorderly that 

 is, ataxic movements. On the histological side it has been shown, 

 as stated above, that these fibers end in nuclei of the medulla, 

 and thence are continued forward by the great sensory tract 

 known as the "lemniscus," to end eventually in that part of the 

 cortex of the cerebrum designated as the area of the body senses. 

 Ascending (Afferent or Sensory) Paths in the Lateral Funiculi. 

 The two best known ascending tracts in these funiculi are those of 

 the cerebellospinal and the superficial anterolateral fasciculi. Both 

 of these tracts are composed of endogenous fibers. The former 

 takes its origin in the lower thoracic region, and is composed of 



axons connected with the tract 

 cells of the dorsal nucleus. The 

 impulses which its fibers con- 

 vey are brought into the cord 

 through those fibers of the 

 posterior root that end around 

 the cells of the dorsal nu- 

 'cleus. A number of the fibers 

 in this funiculus end doubt- 

 less in the gray matter of 

 the upper regions of the cord, 

 but most of them continue 

 upward on the same side, 

 enter the inferior peduncle of 

 the cerebellum (restiform 

 body), and terminate in the 

 posterior and median portions 



of the vermiform lobe, mainly on the same side, but partly also on 

 the opposite side. The superficial anterolateral fasciculus, situ- 

 ated ventrally to the cerebellospinal fasciculus (gr, Fig. 75), 

 may extend forward into the anterior funiculi along the periphery 

 of the cord. The two bundles may be more or less intermingled 



Fig. 78. To show the course of the fibers 

 of the cerebellar tracts of the cord (Moil)'. 

 v.a.c., Ventral tract (superficial anterolateral); 

 d.a.c., dorsal tract (cerebellospinal); s.v., 

 superior verrnis; P.C.Q., inferior colliculus. 



