TEXT-BOOK OF PHYSIOLOGY. 



crossed or decussated at the raphe near the anterior surface of the 

 pons; those contained in the inferior peduncles are the most abundant 

 and important, and are represented by (i) the direct cerebellar tract, 

 which terminates in the superior vermis after decussation; (2) the 

 anterior and posterior arcuate fibers, the former coming from the 

 gracile and cuneate nuclei of the opposite side, the latter from the 

 same side, which also pass to the superior vermis; (3) the acustico- 

 cerebellar tract, composed of fibers the axons of the sensory end 

 nuclei (Deiters) of the vestibular portion of the auditory nerve. It 



is probable that all these fibers de- 

 cussate prior to their final termina- 

 tion. 



The cerebellum through this 

 system of efferent and afferent fibers 

 is brought into relation with many 

 different regions of the cerebrum, 

 pons, medulla, and spinal cord. 

 Each half of the cerebellum is con- 

 nected with the foregoing structures 

 of the same side, but more especially 

 of the opposite side. 



FIG. 231. SECTION OF CERE- 

 BELLAR CORTEX. A. Outer 

 or molecular layer. B. 

 Inner or granular layer. 

 C. White _ matter, a. Cell 

 of Purkinje. b. Small cells 

 of inner layer, c. Dendrites 

 of these cells, d. A similar 

 cell lying in the white 

 matter. 



THE FUNCTIONS OF THE CEREBEL- 

 LUM. 



From the observations of the 

 results of experimental lesions, from 

 analysis of clinico-pathologic facts, 

 and from its comparative anatomic 

 development in different animals, the 

 deduction has been drawn that the 

 cerebellum coordinates and har- 

 monizes the action of those muscles 

 the activities of which are necessary 



to the maintenance of body equilibrium both during station and 

 progression. 



By equilibrium of the body is understood a condition which may 

 be maintained for a variable length of time without displacement, and 

 is possible only so long as a line passing through the center of gravity 

 falls within the base of support. The support offered by the earth 

 to the feet neutralizes and counteracts the force of gravity. In station, 

 when the body is in the erect or military position, the arms by the 

 side, the center of gravity lies between the sacrum and the last lumbar 

 vertebra, and the line of gravity falls between the feet and within 

 the base of support. The entire skeleton for the time being is ren- 

 dered fixed and rigid at all its joints by the combined action of the 



