STRUCTURE AND CONNECTIONS OF MEDULLA OBLONGATA. 



279 



of which one proceeds upwards and forwards to join the Crus Cerebri, 

 thence to pass to the Optic Thalami ; whilst the other passes upwards and 

 backwards into the Corpora Qnadrigemina. 3. Of the true Restiform bodies, 

 the fibres pass entirely into the Cerebellum. 4. Finally, of the Posterior 

 Pyramids, the fibres pass directly onwards through the Crura Cerebri into 

 the Thalami, whence they radiate to the convolutions. 



353. The downward course of these fibres into the Spinal Cord now re- 

 mains to be traced; and their arrangement is by no means a simple one. 1. 

 The Anterior Pyramids decussate, as is well known, at their lower extremity ; 



[Fig. 142. 



Analytical diagram of the encephalon in a vertical section. (After Mayo.) 



i. Spinal cord. r. Restiform bodies passing to, c the cerebellum, d. Corpus dentatum of the cerebel- 

 lum, o. Olivary body. /. Columns continuous with the olivary bodies and central part of the medulla 

 oblongata, and ascending to the tubercular quadrigemina and optic thalami. p. Anterior pyramids, v. 

 Pons Varolii. n, b. Tubercular quadrigemina. g. Geniculate body of the optic thalamus. t. Pro- 

 cessus cerebelli ad testes. a. Anterior lobe of the brain, q. Posterior lobe of the brain.] 



the principal part (but not the whole) of the fibres on each side, passing over 

 to the other. The decussating fibres pass backwards as well as downwards, 

 and enter, not the anterior column of the spinal cord, (as commonly stated,) 

 but the lateral column. The smaller bundle of fibres, which do not decus- 

 sate, passes downwards, along with those of the olivary bodies, to form the 

 anterior column. 2. The fibres descending from the Olivary bodies converge 



