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HANDBOOK OF PHYSIOLOGY. 



the restiform bodies. On the outer side of the anterior pyramids of each 

 side, near its upper part, is a small oval mass containing gray matter, 

 and named the olivary body; and at the posterior part of the restiform 

 column immediately on each side of the posterior median groove, con- 

 tinuous with the posterior median column of the cord, a small tract is 

 marked off by a slight groove from the remainder of the restiform body, 

 and called the posterior pyramid or fasciculus gracilis. The restiform 

 columns, instead of remaining parallel with each other throughout the 

 whole length of the medulla oblongata, diverge near its upper part, 

 and by thus diverging, lay open, so to speak, a space called the fourth 

 ventricle, the floor of which is formed by the gray matter of the interior 

 of the medulla, exposed by this divergence. 



FIG. 336. 



FIG. 335. Anterior surface of the pons Varolii, and medulla oblongata. a, a, anterior pyra- 

 mids; &, their decussation; c, c, olivary bodies; d, d, restiform bodies; e, arciform fibres; /, fibres 

 passing from the anterior column of the cord to the cerebellum; g. anterior column of the spinal 

 cord; h, lateral column; p, pons Varolii; i, its upper fibres; 5, 5, roots 9f the fifth pair of nerves. 



FIG. 336. Posterior surface of the pons Varolii, corpora quadrigemina, and medulla oblongata. 

 The peduncles of the cerebellum are cut short at the side, a, a, the upper pair of corpora quadri- 

 gemina; 6, 6, the lower; /, /, superior peduncles of the cerebellum; c, eminence connected with the 

 nucleus of the hypoglossal nerve: e, that of the glosso-pharyngeal nerve: i, that of the vagus nerve; 

 d, d, restiform bodies; p, p, posterior pyramids; v, v, groove in the middle of the fourth ventricle, 

 ending below in the calamus scriptorius; 7, 7, roots of the auditory nerves. 



On separating the anterior pyramids, and looking into the groove be- 

 tween them, some decussating fibres of the lateral columns of the cord 

 can be plainly seen. 



Distribution of the Fibres of the Medulla Oblongata. 



a. The anterior pyramid ef each side, although mainly composed of 

 continuations of the fibres of the anterior columns of the spinal cord, 

 receives fibres from the lateral columns, both of its own and the opposite 

 side; the latter fibres forming almost entirely the decussating strands 



