716 THE BRAIN. 



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 internun- 

 cial 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 probably 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 ( 592) ; but in reference 

 to this too, beyond its probable connection with the auditory sensations 

 ( 589), we lack evidence. 



A conspicuous part of the brain, namely, the cerebellum, naturally ar- 

 rests 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 prac- 

 tically 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 affer- 

 ent 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 shows 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 ( 531), may be compared to an outlying part of the cere- 

 bellar tract, certainly continue uncrossed into the peduncle of the same 

 side. We may conclude, therefore, that the ties of the cerebellum with 

 the posterior roots are both crossed and uncrossed. And we may regard 

 this double grip of the cerebellum on the cord, this grip oil both sides of 

 it, as an additional evidence that the ties of the cerebellum with the 

 spinal cord are not merely for the purpose of serving as the channel for 

 the impulses of muscular sense, but are the means by which the cere- 

 bellum transforms or elaborates sensory impulses, not of muscular sense 

 alone or chiefly, but probably of all kinds, in order that they may take 

 part in cerebral operations, of which the coordination of bodily move- 

 ments may be one, but probably is only one, of several or even of many. 



SOME OTHER ASPECTS OF THE FUNCTIONS OF THE BRAIN. 



599. It is difficult to say anything definite concerning the transmis- 

 sion of sensory impulses and the development of sensations ; it is still more 

 difficult to say anything definite, beyond what has been already incidentally 

 said, concerning the parts played in the work of the brain by the various 

 aggregations of gray matter and tracts of fibres forming the middle part of 

 the brain. Neither experiment nor clinical study has as yet afforded any 

 clear or sure leading. 



To what has already been said about the cerebellum, we may add the 

 following ; 



Electrical stimulation of the surface of the cerebellum, in the monkey 

 and in other animals, has led to movements of the eyes, and of other 

 parts of the head ; but we cannot from such results draw any satisfactory 

 inferences. 



