340 THE BODY AT WORK 



(p. 303). To these must be added the stellate, bracketing cells 

 of the molecular layer, the axons of which divide to form baskets 

 about a number of Purkinje-cells, and the cells of Golgi of 

 the granular layer. These last are comparatively large cells, 

 which have thornless dendrites, and axons which branch re- 

 peatedly in the granular layer, without passing into the white 

 matter which underlies the cortex. Two kinds of nerve-fibre 

 bring impulses to the cortex : (1) " Mossy " fibres, which bear 

 rosettes of filaments which distribute impulses to the granules ; 

 and (2) " climbing " fibres or " tendril " fibres, which, passing 

 through the granular layer, cling like ivy to the trunk and 

 principal boughs of the dendritic processes of Purkinje-cells. 

 The axons of the cells of Purkinje undoubtedly carry impulses 

 away from the cortex, but their destination is not certainly 

 known. 



The uniformity of structure of the cerebellum suggests that 

 it " acts as a whole." Anatomy gives no warrant for the 

 expectation that work of different kinds is done by its several 

 lobes. Its simplicity leads one to hope that its mechanism 

 may some day be understood ; but at present there are so many 

 gaps in our knowledge that it is difficult, perhaps hardly profit- 

 able, to attempt to string together the few anatomical facts of 

 which we are sure. 



By means of tracts of afferent fibres the cerebellum has a 

 very extensive connection with the grey matter of the cerebro- 

 spinal axis (including the optic thalamus) into which sensory 

 impulses of all kinds are poured. Experimental results indi- 

 cate that the organ distributes impulses to the whole length of 

 the cerebro-spinal axis, from the level of the neurones which 

 govern the muscles which move the eyes to its far hinder snd. 

 No nerve-roots enter it. Its afferent fibres are the axons of 

 cell-bodies which lie in the posterior horns of the grey matter 

 of the spinal cord and in the corresponding grey matter of the 

 axis of the brain, especially that part related to the nerve from 

 the semicircular canals. Another set of afferent fibres lies 

 at the periphery of the spinal cord, forming one of the best 

 defined of the spinal tracts. It is also one of the oldest, being 

 found in the same situation in all vertebrate animals. Its 

 fibres, which are exceptionally large, are the axons of cells 

 which form a very definite column the " vesicular column of 



