THE MEDULLA OBLOXGATA. 



145. 



umns of the cord. Ascending, they enter the cerebellum, and The restifbrm 

 are continuous with the inner part of its cms. They there- k die s- 

 fore are a tract of communication from the spinal cord to the cerebellum. 

 They each inclose a gray nucleus, which is the ganglion of the pneumo- 

 gastric nerves, and of some of the roots of the glosso-pharyngeal. 



Fourth. The posterior pyramids are doubtfully marked off from the 

 restiform bodies in front, and are separated from each other The posterior 

 by the posterior fissure. Superiorly, their fibres are contin- pyramid*. 

 uous with the sensory tract of the crura cerebri : their gray nuclei are 

 the ganglia of the auditory nerves. 



The structure of the medulla oblongata is exempli- 

 fied in the annexed figures. 



Fig. 145: 1, chiasm of the optic nerves; 2, crus cere- 

 bri ; 3, tuber cinereum ; 4, corpora albicantia ; 5, locus 

 .perforatus ; 6, pons varolii ; 7, section of the middle 

 peduncle of cerebellum ; 8, transverse fissure, separa- 

 ting the medulla from the pons ; 9, first enlargement 

 of the cord, or medulla oblongata ; 10, anterior pyra- 

 mid; 11, olivary body; 12, anterior portion of resti- 

 form body ; 13, neck of the medulla oblongata; from 

 16 downward is the anterior median fissure; from 17 

 downward, the anterior lateral furrow. 



Fig. 146: 1, section of optic 

 tract; 2, tubercula quadrigemina ; 

 3, triangular band ; 4, section of crus cerebelli ; 5, 

 medulla oblongata ; 6, anterior floor of the fourth ven- 

 tricle ; 7, median fissure of the fourth ventricle, aid- 

 ing to form the calamus scriptorius ; 8, mammillary 

 swelling near the nib of the pen ; 9, posterior portion 

 of the restiform body; from 12 down- 

 ward, posterior median fissure ; from 

 13 downward, lateral furrow ; from 14 

 downward, posterior furrow. 



T-T. * i / ^ t> , i 



Juig. 147: o, anterior column ot the 

 cord, divided superiorly into two portions, of which the 

 most internal one contributes to the formation of the cor- 

 responding pyramid; 7, middle or lateral column, di- 

 vided superiorly into three or four portions, decussating 

 with as many portions of the column of the opposite side, 

 the decussation taking place both laterally and antero- 

 posteriorly : it is the origin of the internal two thirds 

 of the pyramid ; 8, 8, pyramids ; 9, white fibres of the 

 pyramid, traversing the pons, and continuing to the crus 

 'U 



Fig. 140. 



Front of medulla ob- 

 longata. 



Fig. 147. 



Posterior view of medulla 



