CHAP, ii.] THE BRAIN. .so? 



ends in the bulb, and is not continued on directly to the cortex. 

 And possibly it does play a somewhat analogous part, in so far 

 as it serves as a special connection between the brain and the 

 whole series of spinal nerves. But we are wholly ignorant as 

 to what it really does ; and whatever be the exact nature of the 

 part which it plays, there is no adequate evidence either from 

 clinical histories or from experiment that it has relations to one 

 kind of sensation only. It has indeed been supposed by some 

 to be especially a tract for the impulses of the muscular sense ; 

 but neither experiment nor clinical study affords adequate 

 proof of this view. The condition known as locomotor ataxy, 

 the salient feature of which is loss or impairment of muscu- 

 lar sense, is associated with disease of the posterior root and 

 of its entrance into the cord, not with disease confined ex- 

 clusively to the median posterior column. Moreover the tract 

 cannot carry all the impulses of muscular sense, since some 

 of them must pass at once into the grey matter, to take part 

 in the coordination of reflex movements, and must therefore 

 travel by fibres which do not form this tract. Similarly is there 

 no adequate proof of the tract being an exclusive channel for 

 tactile or for painful sensations. Possibly it has some special 

 relations to all the different kinds of sensation. 



We may also perhaps urge similar considerations with regard 

 to the cerebellar tract, which though starting from a relay of 

 grey matter is thence onward to the cerebellum a continuous 

 tract. This tract also has been supposed to carry impulses of 

 a special kind, and more particularly those of muscular sense. 

 But even admitting that the tract does convey impulses derived 

 from the muscles and their appendages, which impulses the 

 cerebellum makes use of in N its work of coordinating movements, 

 especially those concerned in equilibrium, it cannot be the chan- 

 nel for the ordinary impulses of muscular sense, since these 

 remain after total removal of the cerebellum. Nor does either 

 experiment or clinical study afford in other ways any clear 

 proof that this tract is solely or even especially concerned with 

 the muscular sense. 



With regard to the antero-lateral or other ascending tracts 

 our knowledge is too imperfect to justify us in supposing that 

 any one is the special or exclusive channel for any one kind 

 of sensation, or indeed in drawing any conclusions at all con- 

 cerning it. 



But when we subtract from the white matter of the cord 

 these continuous tracts of ascending degeneration of presumably 

 sensory or afferent function, and the continuous tracts of descend- 

 ing degeneration, which we may confidently speak of as motor 

 or at least efferent, there are left only the fibres which we may 

 suppose to be longitudinal commissural or internuncial fibres 

 between successive segments. We are thus driven to the pro- 



