62O 



THE NERVOUS SYSTEM 



restiform body, etc. These cells, being stimulated, send the impulses by their 

 axis-cylinders to the molecular layer, and through their T-shaped divisions to 

 the dendrites of the cells of Purkinje. Thence an impulse is sent out by the 

 axis-cylinder process of this cell. Other ascending impulses are brought up 

 by those fibers which pass directly to the molecular layer and send their ter- 

 minals winding around the dendrites of the cells of Purkinje. Prob- 

 ably impulses pass up also through the ascending fibers which affect the 

 basket cells, and, through them and their basket-like terminals, the cells of 

 Purkinje. Purkinje cells send cerebeilar motor fibers to the nucleus dentatus 



Stellate 



molecular 

 layer 



'""-^^ 



granule 



granule 



FIG. 387. A, Afferent fiber to basket (stellate) cell; B, neuraxone of Purkinje cell; C, 

 afferent fiber to Purkinje cell; D, afferent (mossy) fiber to granule cell. 



cerebelli and through the superior peduncles to the red nucleus and the 

 thalamus, and to the ventro-lateral descending tract of the cord, to end 

 about the anterior horn cells. 



Functions of the Cerebellum. With the exception of its middle 

 lobe, the cerebellum is itself insensible to irritation and may be all cut away 

 without eliciting signs of pain (Longet). Its removal or disorganization by 

 disease is also generally unaccompanied by loss or disorder of sensibility; 

 animals from which it is removed can smell, see, hear, and feel pain, to all 

 appearances, as perfectly as before (Flourens; Magendie). It cannot, there- 

 fore, be regarded as a principal organ of sensation. Yet if any of its crura 

 be touched, pain is indicated; and, if the restiform tracts of the medulla 

 oblongata be stimulated, the most acute suffering appears to be produced. 



These phenomena may properly be ascribed to the activity of the cerebral 

 cortex, since the number of collaterals on the fibers that pass to cerebeilar 

 tracts is very great, and impulses arising from their stimulation may reach 

 the sensorium by paths other than through the cerebellum. 



