PHYSIOLOGY OF THE NERVOUS SYSTEM 317 



gestion and circulation. These neurons are controlled for the most part 

 by fibers from the bulb and spinal cord, and cannot for this reason be 

 looked upon as forming an independent system. Their chief purpose 

 seems to be that of spreading the influence of neurons from the central 

 system over a wider area than they would otherwise reach. For ex- 

 ample, a single neuron passing out from the spinal cord may, by termi- 

 nating in a. sympathetic ganglion, stimulate a large number of neurons, 

 each of which will in turn stimulate the cells of muscles or of glands. 

 Because of this function, the sympathetic neurons are sometimes called 

 distributing neurons. 



Functions of the Cerebellum. Efforts to discover some special func- 

 tion of the cerebellum have been in the main unsuccessful. Its removal 

 from animals, instead of producing definite results, usually interferes in 

 a mild way with a number of activities. The most noticeable results 

 are a general weakness of the muscles and an inability on the part of 

 the animal to balance itself. This and other facts, including the man- 

 ner of its connection with other parts of the nervous system, have led 

 to the belief that the cerebellum is the chief organ for the reflex coordi- 

 nation of muscular movements, especially those having to do with the 

 balancing of the body. In this connection it is subordinate to and un- 

 der the control of the cerebrum. Of the relations which the cerebellum 

 sustains to the cerebrum and to the different parts of the body, the fol- 

 lowing view is quite generally held : 



In the development of secondary reflexes, as already described, 

 conditions are established in the cerebellum, such that given stimuli 

 may act reflexhiely through it and produce definite results in the way 

 of muscular contraction. After the establishment of these conditions, 

 afferent impulses from the eyes, ears, skin, and other places, under the 

 general direction of the cerebrum, may cause such actions as the bal- 

 ancing of the body, walking, etc., as well as the delicate and varied 

 movements of the hand. This view of its functions makes of the cere- 

 bellum the great center of secondary reflex action. 



Functions of the Cerebrum. While the work of the 

 cerebrum is closely related to that of the general nervous 

 system, it, more than any other part, exercises functions 

 peculiar to itself. The cerebrum is the part of the nervous 

 system upon which our varied experiences leave their im- 

 pressions and through which these impressions are made 



