THE SPINAL CORD. 



677 



Fig. 178. 





specially destined to afford the conditions requisite for the performance of the 

 functions of Respiration and Deglutition, instead of exerting its reflex power in 

 the ordinary locomotive actions of the body; but the arrangement of its fibrous 

 strands and of its nuclei of gray matter is peculiar ; and a brief notice of its 

 structure, and of the connections of its parts, is consequently desirable. Four 

 principal strands of nerve-fibres may be distinguished in each of its lateral 

 halves; these are I. The Anterior Pyramids or Corpora Pyramidalia ; 

 n. The Olivary Bodies, or Corpora Olivaria; in. The Restiform Bodies, or 

 Corpora Restiformm / otherwise called Processus a Cerebello ad Medullam 

 Oblongatam; iv. The Posterior Pyramids, or Corpora Pyramidalia Pos- 

 terwra. The connections of these with the Brain above, and with the Spinal 

 Cord below, will be presently traced. 1 The vesicular substance, on the other 

 hand, is principally aggregated in three pairs of ganglionic centres; of which 

 the anterior forms the nucleus of the Olivary body, the lateral of the Restiform, 

 and the posterior of the Posterior Pyramidal. 



711. The Anterior Pyramids (i) consist entirely of fibrous structure, and 

 establish a communication be- 

 tween the " motor tract" (Fig. 

 178, m t) of the Crura Cerebri, 

 and the anterior and antero- 

 lateral columns of the Spinal 

 Cord. The principal part of 

 their fibres decussate ; and these, 

 as they pass from above down- 

 wards, dip away from the ante- 

 rior surface of the Cord, and 

 connect themselves with its mid- 

 dle or lateral columns, instead 

 of with its anterior, as was 

 pointed out by Rosenthal, 2 and 

 more fully described by Dr. 

 J. Reid. 3 A small part of the 

 fibres of the pyramidal columns, 

 however, do not decussate, but 

 proceed downwards on the same 

 side, into the corresponding an- 

 terior columns of the Spinal 

 Cord. ii. The Olivary bodies 

 are composed of fibrous strands, 

 enclosing a gray nucleus (Fig. 

 178, off) on either side. The 

 upward continuation of the for- 



Dissectionof the Medulla Oblongata,io show the connections 

 of its several strands : A, corpus striatum ; B, thalamus op- 

 ticus; c, D, corpora quadrigcmina; E, commissure connect- 

 ing them with the cerebellum ; F, corpora restifonnia ; P, P, 

 pons varolii; st, st, sensory tract; mt, mt, motor tract; g, 

 olivary tract ; p, pyramidal tract; oy, olivary ganglion; op, 

 optic nerve ; 3 m, root of the third pair (motor) ; 5 , sensory 

 root of the fifth pair. 



1 Great diversities will be found in the accounts given of those connections by different 

 authors ; some of which are attributable to a variation in the use of terms, which must 

 not pass unnoticed. By the majority of Anatomists, the name of Corpora Restiformia is 

 given to the Cerebellar Columns ; and this designation, therefore, it seems advisable to 

 retain. Some, however, and amongst them Dr. J. Reid, in his very excellent description 

 of the Anatomy of the Medulla Oblongata ("Edinb. Med. and Surg. Journal," Jan. 1841), 

 give that name to the columns that pass up from the posterior division of the spinal cord 

 into the crus cerebri which are here called (after Sir C. Bell) the posterior pyramids ; 

 and apply the term Posterior Pyramids to the Cerebellar column. The truth is that, as 

 Sir C. Bell has justly observed, all the tracts of fibrous matter connecting the Brain with 

 the Spinal Cord have a somewhat pyramidal form ; and it might be added that all have 

 something of a restiform or cord-like aspect. 



2 "Ein Beitrag zur Encephalatomie," Weimar, 1815. 



3 "Edinb. Med. and Surg. Journ.," Jan. 1841 ; and "Physiol., Pathol., and Anat. Re- 

 searches," CHAP. VII. 



