CHAP, ii.] THE BRAIN. 1107 



of grey matter, and the several strands and tracts of fibres which 

 we briefly described in a previous section, must have of course a 

 meaning ; but it may be doubted whether we have even so much 

 as a correct glimpse of that meaning in any one case, if we except 

 those which are in immediate connection with the cranial nerves 

 and their nuclei. Seeing that the thalamus appears on the one 

 hand to be connected with all or nearly all parts of the cortex, 

 and on the other hand to serve as the front of the tegmental 

 system, it is tempting to suppose that it plays an important part 

 in sensations pertaining to the body generally, as part of it, the 

 pulvinar, certainly .does with reference to the special sense of 

 sight ; but we have no decisive indications as to what part it plays. 

 And the part which it plays, whatever that may be, is not an 

 exclusively sensory one, since both experimental and morbid lesions 

 of the thalamus are apt to produce disorders of movement as well 

 as other efferent effects. We ought perhaps to say the parts 

 which it plays ; for it is a complex body, having many ties and 

 probably performing many duties. 



The conspicuous fillet again, seeming as it does to be a special 

 internuncial tract connecting what appear to be more particularly 

 afferent or sensory parts of the bulb, such as the gracile and 

 cuneate nuclei, with various parts of the middle brain and pro- 

 bably with the cortex, presents itself as a probable path of 

 sensations of one kind or another from the body at large, the 

 " narrow path " of the anatomical programme ( 680) ; but in 

 reference to this too, beyond its probable connection with the 

 auditory sensations ( 677), we lack evidence. 



A conspicuous part of the brain, namely the cerebellum, 

 naturally arrests our attention on account of its large connections 

 with what appear to be afferent structures ; in the anatomical 

 programme, we called it "the broad path." By the cerebellar 

 tract it has an uncrossed grip upon what is practically the 

 whole length of the spinal cord ; by the other constituents of 

 the inferior peduncle it has a like uncrossed grip upon what 

 appear to be afferent structures in the bulb, the gracile and 

 cuneate nuclei, as well as on the eighth (vestibular) nerve and 

 probably representatives of other afferent cranial nerves ; it has 

 further a crossed grip through the gracile and cuneate nuclei on 

 the afferent posterior columns of the whole cord. It is of course 

 possible that the cerebellar tract, though in itself uncrossed, lays 

 its hand, by means of the vesicular cylinder for instance, on 

 impulses which have already crossed from the posterior roots 

 of the other side ; for as we have seen the evidence as a whole 

 shews that sensory impulses do cross over; but neither has the 

 crossing of the impulses been definitely proved, nor has the path 

 of the crossing been clearly demonstrated ; while, on the contrary, 

 the fibres of the auditory nerve which pass to the cerebellum, and 

 which as we have suggested ( 618), may be compared to an 



