CH. XLVII.] REFLEX ACTIONS. 659 



Some afferent impulses reach the cerebellum via the cells of 

 Clarke's column and the direct or dorsal cerebellar tract to the 

 restiform body arid inferior peduncle of the cerebellum. It 

 terminates in the vermis or middle lobe of the cerebellum ; the 

 fibres of the tract of Gowers originate in the same cells, and those 

 of its fibres which enter the cerebellum do so by its superior 

 peduncle, and these also end in the vermis. 



This leaves us still one more set of fibres to consider ; these 

 are the fibres that leave the cerebellum and travel up to the brain 

 and down the cord. They, like most of the other tracts, have been 

 investigated by the degeneration method. Their exact course is, 

 however, uncertain, though probably they ultimately terminate by 

 arborising round the multipolar cells of the cerebrum and of the 

 anterior horn of the cord (see fig. 484, p. 651; see also under 

 Cerebellum, Chapter XLIX). 



Reflex Action of the Spinal Cord. 



There are two theories of a speculative nature regarding the 

 relationship of reflex and voluntary actions : one is, that all 

 actions are in essence reflex, and that the so-called voluntary 

 actions are modified reflexes, in which the afferent impulse to act, 

 though often obscure, is nevertheless by seeking always to be 

 found. Put in popular language, this theory implies that we 

 have really no such thing as a will of our own, but our actions 

 are simply the result of external circumstance?. 



The other theory is the exact opposite namely, that all 

 actions are in the beginning voluntary, and become reflex by 

 practice in the lifetime of the individual, or the lifetime of his 

 ancestors, who transmit this character to their descendants. 



This is not the place to discuss a philosophical question of 

 this kind, and still less the debated question whether acquired 

 characters are transmissible by inheritance. The distinction be- 

 tween voluntary and reflex actions is a useful practical one, and 

 certainly it cannot be doubted that many practised actions 

 become reflex in the lifetime of every one of us. Take walking as 

 an example : at first the act of locomotion is one in which the 

 brain is concerned ; it is an action demanding the concentration 

 of the attention ; but later on the action is largely carried out by 

 the spinal cord, the afferent impulses to the cord from the feet 

 directing the efferent impulses to the muscles concerned. 



The reflex actions of the spinal cord may first be studied in a 

 brainless frog, as in this animal the spinal cord possesses a great 

 power of controlling very complex reflex actions. 



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