STRUCTURE OF THE MEDULLA OBLONGATA. 



607 



continuation of the former divides, while passing through the Pons Varolii, 

 into two bands, one of which proceeds upwards and forwards as a part of the 

 "motor tract" (m t) of the Cms Cerebri, whilst the other (o) proceeds upwards 

 and backwards to reach the Cor- 

 pora Quadrigemiua (C,D). The FIG. 213. 

 Olivary columns are continu- 

 ous interiorly with the antero- 

 lateral columns of the Spinal 

 Cord. Their vesicular nucleus, 

 which is known as the " Corpus 

 dentatum," and which appears 

 first amongst the network of 

 fibres into which the anterior 

 cornu is resolved and the outer 

 portion of the anterior column 

 seems to be intimately connected 

 with all the surrounding parts 

 of the Medulla, chiefly through 

 the arciform system, which will 

 presently be described ; and Mr. 

 Loekhart Clarke, though he has 

 never been able to trace any im- 

 mediate connection between the 

 cells of the nuclear lamime and 

 the roots of the nerves even 

 in the case of the hypoglos- 



Sal nerves which paSS directly og, olivary ganglion; op, optic nerve; 3m, root of the 

 through them yet is inclined tO third P air (motor) ; 5 s, sensory root of the fifth pair. 



regard them as the co-ordinating 



centres for the different ganglia or nuclei of the Medulla Oblongata. 1 Schroder 

 v. d. Kolk is disposed from many considerations to regard these bodies as the 

 nervous centres on which the symmetrical movements required ki speech or 

 the articulation of the voice are essentially dependent.' 2 m. The lateral 

 columns (lc, Fig. 212), Faisceaux intermedia-ires of Longet, decussate below 

 with the anterior pyramids. Ascending, they assume the form of triangular 

 columns, the apex of each appearing at the surface, the base being opposed 

 to the one of the opposite side, and projecting, covered with gray substance, 

 into the floor of the fourth ventricle. Behind, they are in contact with the 

 restiform bodies, and in front with the olivary bodies. At their upper part 

 they trifurcate, one portion curving outwards to enter the middle peduncle 

 of the cerebellum, the other two separating from one another to allow of the 

 passage of the superior peduncles of the cerebellum and part of the resti- 

 form columns, the inner one ultimately reaching the cerebral peduncles ; 

 the outer one forms a transverse commissure behind the Corpora Quadri- 

 gemiua. iv. The gray tubercle of Rolando (t c, Fig. 213) is simply the ex- 

 panded extremity of the posterior coruu of the gray substance of the Spinal 

 Cord, now appearing on the surface. v. The Restiform bodies each consists 

 of fibrous strands (F, Fig. 213) inclosing a gray nucleus. The fibrous 

 strands pass upwards into the Crura Cerebelli ; whilst below they are chiefly 

 continuous with the ])osterior columns of the Spinal Cord, having also some 

 connection with the posterior part of the middle columns. These Cerebellar 

 columns, moreover, communicate with the anterior columns of the Spinal 



Dissection of the Medulla Oblongata, to show the con- 

 nections of its several strands: A, corpus striatum; B, 

 thalaimis options; c, D, corpora quadrijiemina: E, com- 

 missure connecting them with the cerebellum ; F, corpora 

 restiformia; P, P, pons Varolii; si, s t, sensory tract; 

 n I, m I, motor tract ; g, olivary tract ; p, pyramidal tract ; 



Op. cit., p. 245. 



Op. cit., p. 148 et seq. 



