OTHER ASPECTS OF THE FUNCTIONS OF THE BRAIN. 717 



The removal of various parts of the cerebellum, especially of the 

 medium parts, has led to a want of coordination in bodily movements ; 

 and an unsteady gait, due to a like want of adequate coordination, is a 

 frequent symptom of cerebellar disease. But the incoordination which 

 makes its appearance immediately after removal of, or injury to, the cere- 

 bellum may eventually disappear, even though large portions have been 

 removed ; and many cases of cerebellar disease have been recorded in 

 which the most perfect coordination of movements was retained. Hence, 

 the results of experimental and clinical study, while on the whole support- 

 ing the conclusion that the cerebellum has in some way 'to do with coor- 

 dination, throw little or no light on the exact nature of the part which the 

 organ plays in the complex process, but perhaps rather show that we are 

 at present wholly ignorant of how coordination is brought about. 



Many hypotheses have been put forward as to the work carried out by 

 the cerebellum, but none of these can be said to have an adequate basis. 

 And, indeed, if there be any value in the reflections we have repeatedly 

 made in previous pages, the physiologist ought not to use the words " func- 

 tions of the cerebellum." From a physiological point of view it is, so to 

 speak, a matter of accident that various structures, the seats of various 

 physiological processes, have, from morphological causes, been gathered 

 together into the body which anatomists call the cerebellum. The task 

 of the physiologist is to unravel the ties binding these various cerebellar 

 structures with other parts of the central nervous system, and so with 

 various parts of the body at large. 



We must content ourselves here with calling attention to two or three 

 broad and suggestive facts concerning its structure and connections. 



In the first place, one striking fact about the cerebellum is the very large 

 development of commissural fibres connecting together the superficial gray 

 matter of the two hemispheres for the greater part of their extent, and 

 passing, not only tjirough the pons ( 548) as part of the middle peduncle, 

 but also through the median vermis. This great commissure is second only 

 to the great callosal commissure of the cerebrum ; and from the fact that 

 median lesions of the cerebellum, those which do most damage to this com- 

 missure, are the most effective in causing incoordination and forced move- 

 ments, we may infer that it in some way plays an important part in co- 

 ordination. 



A second striking fact is one on which we have already just dwelt, the 

 connection, chiefly an uncrossed one, through the inferior peduncle, with the 

 afferent structures of the bulb and spinal cord. We may now add that the 

 fibres of this peduncle passing into the centre of the white matter of the 

 cerebellar hemisphere of the same side enclose the gray matter of the nu- 

 cleus deutatus and appear largely to end in that body, though some pass 

 on to the vermis. 



A third striking fact is the connection, this being, as far as we know, 

 wholly a crossed one, through the pons and pes, with the cerebral cortex 

 both of the extreme frontal region and of the temporo-occipital region 

 and possibly or even probably with more scattered cortical elements of the 

 parietal (motor) region. This connection is one between cortex and cortex, 

 or, at least, between cerebral cortex and cerebellar superficial gray matter, 

 for the fibres of the middle peduncle passing from the gray matter of the 

 pons which serves as a relay end in the surface of the lateral hemisphere 

 of the cerebellum. The frontal cortical fibres passing to the pes have a 

 descending degeneration, that is, from the cortex to the pons, and we may 

 probably assume that the similar temporo-occipital fibres similarly degener- 

 ate downward to the pons ( 545). From this it has been inferred that 



