280 SCIENCE PROGRESS. 



One of the chiefest functions of the cerebellum is, Luciani 

 says, to exert by each of its own lateral halves on the so- 

 called motor region (sfera sensorio-motrice) of the opposite 

 cerebral hemisphere an influence comparable with the 

 ''bracing" action exerted by the centripetal stream 

 which debouches from the sensory spinal nerve-root into 

 the anterior cornu of the spinal cord, and maintains in 

 the nerve-cells of the latter a steady gentle discharge 

 into the skeletal muscles, the basis of the reflex muscular 

 tone. 



As to the details of the labour of the supreme hemi- 

 spheres themselves, it may be said that Munk's researches 

 in this subject last year reached a standpoint especially 

 inviting retrospection. Of all the experimenters who early 

 followed in the wake of Fritsch and Hitzig's 1 notable 

 discovery, Munk, 2 with the exception of Hitzig 3 himself, 

 perhaps alone seized and described the phenomena in a 

 way which has not since required fundamental modification, 

 or indeed any modification at all further than that involved 

 in the filling in of detail. He from the first (1877) described 

 the cerebral cortex as a congeries of centres, whose spatial 

 arrangement has sufficient differentiation to allow of their 

 being grouped topographically in terms of sensory avenues 

 by which each group lies easiest of access. Thus the 

 sehsphdre or group of centres accessible via the optic nerve, 

 the horspkdre accessible via the auditory nerve, and so on. 

 The sphdre is excitable not only indirectly, e.g., via retina; 

 stimuli applied to its intrinsic fibres are efficient and elicit 

 for instance definite consensual movements of the eyeballs. 

 Conversely in consequence of destruction of a sphdre specific 

 sensory reactions, e.g., those via retina, suffer damage or 

 drop out entirely. 



For Munk, as for its discoverer Hitzig, the parietal 

 region of cortex whence can be elicited movement of the 



1 Du Bois-Reymond's Archiv, 1870. 



2 Ibid., 1878. 



8 Untersuchnngen ueber das Gehirn, Berlin, 1874. 



