THE VESTIBULAE APPARATUS AND CEREBELLUM 193 



branch of government, interpreting the decrees of the legislative 

 centers, integrating the behavior by combining its elements into 

 cooperating systems in view of all the factors of present and 

 past experience, ,and with extensive powers of veto over inap- 

 propriate reactions which may have been inaugurated by the 

 lower centers. The cerebellum is the great administrative 

 office which attends to the details of the proper execution of the 

 acts which have been previously determined upon and initiated 

 in the other departments of government. 



Summary. The vestibular apparatus and the cerebellum are 

 genetically and physiologically very closely related. The semi- 

 circular canals are the most highly differentiated proprioceptive 

 end-organs, serving chiefly the functions of equilibration and 

 the maintenance of muscular tone. These reactions are, for the 

 most part, unconsciously performed and there is no important 

 cortical path from the vestibular nuclei. These nuclei effect 

 reflex connections with the motor centers of the spinal cord and 

 medulla oblongata, especially the eye-muscle nuclei, and with the 

 cerebellum. 



The cerebellum has been developed out of the primary vestibu- 

 lar area for the more perfect coordination and integration of the 

 somatic motor reactions and for strengthening these reactions. 

 It receives afferent fibers from all somatic sensory centers, and 

 in mammals it is also very intimately connected with the cere- 

 bral cortex, these two higher centers appearing always to act 

 conjointly. The cerebellum discharges into all of the somatic 

 motor centers and assists in preserving the proper balance of 

 muscular contraction and in the maintenance of muscular tone. 



LITERATURE 



For the original sources of the data presented in this and the preceding 

 chapters see the bibliographies appended to Chapters VII, VIII, IX, and X. 

 On the cerebellum see further: 



ANDRE-THOMAS and DURUPT, A. 1914. Localisations cerebelleuses, 

 Paris. 



BIANCHI, A. 1903. Sulle vie di connessione del cervelletto, Arch, di 

 Anat. e Embriol., vol. ii. 



BOLK, L. 1906. Das Cerebellum der Saiigethiere, Jena. 



BRUCE, A. N. 1910. The Tract of Cowers, Quart. Jour. Exp. Physiol., 

 vol. iii, pp. 391-407. 



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