FUNCTIONS OF THE BRAIN. 



813 



certain of the fibres of the lateral columns of the cord, and so enable the 

 medulla, by bringing it into communication with impressions coming 

 from below, to act as a reflex centre. The transverse fibres of the 

 medulla are to be regarded as commissural fibres connecting the two 

 halves of the medulla, especially the olivary bodies. 



Closely allied to the anterior surface of the olivary columns are to 

 be found the gray nuclei, or the column of Goll {Keihtring), from which 

 originate the arciform fibres, or the external transverse fibres which 

 surround the entire external surface of the medulla to unite with the 

 ' internal transverse fibres, from there 

 to pass into the restiform bodies, and 

 from there to the cerebellum. 



The internal interweaving of 

 the centrifugal and centripetal 

 fibres, the presence of numerous 

 ganglionic cells, and, to a certain 

 extent, the evident union of different 

 classes of nerve-elements, the sym- 

 metrical connection by transverse 

 fibres of both halves of the medulla, 

 all speak in the clearest way as to 

 the high physiological importance of 

 this portion of the central nervous 

 system, both as the seat of reflex 

 centres, as the origin of numerous 

 •cranial nerves, and as the paths of 

 ■communication from the spinal cord 

 to the brain. 



As is evident from the anatom- 

 ical description of the medulla, in 

 many respects it forms the most 

 important part of the central ner- 

 vous system. It forms the ganglionic 

 termination of a large number of 

 fibres; most of the cranial nerves 

 find in it their origin, and in it the most diverse svstems of the animal 

 body are brought into nervous connection. For the ascending motor 

 and sensory nerves of the spinal cord it forms not only the means of 

 conduction, but is the seat of important centres of co-ordination. These 

 paths, and the most important centres, are represented in diagrammatic 

 form, in Pigs. 353 and 354. 



It has been seen that when the spinal cord is divided below the level 

 of the medulla oblongata in the frog it remains perfectly motionless and 



Fig. 352.— Section of the Medulla Ob- 

 longata AT THE SO-CALLED UPPER 



Decussation of the Pyramids. 

 (Landois.) 



f.l.a., anterior, ft.l.p., posterior median fissures; 

 n.XI, nucleus of the aecessorius vagus; n.XII, nucleus 

 of the hypoglossal ; d.a., the so-called superior or anterior 

 decussation of the pyramids; py, anterior pyramid; 

 n.ar., nucleus arciformis ; ol, median parolivary body; 

 o, beginning of the nucleus of the olivary body; n.L, 

 nucleus of the lateral column; F.r., fcrmutio reticularis ; 

 a, substantia gelatinosa, with (a.V.) the ascending root 

 of the trigeminus ; ?(.<■., nucleus of the funiculus cuneatus ; 

 n.r.l, external nucleus of the funiculus cuneatus; n.a., 

 nucleus of the funiciilus gracilis (or clava) ; -ffl, funiculus 

 gracilis ; II", funiculus cuneatus ; c.c, central canal ; fa, 

 /a, 1 fa,- external arciform fibres. 



