FUNCTIONS OF THE BKAIN. 



813 



Sip 



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

 medulla, by bringing it into communication with impressions coining 

 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 (Keil string), 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 b.y transverse 

 fibres of both halves of the medulla, 

 nil speak in the clearest way as to 

 the high ph}'siological 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 FlG * 

 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 n.e.i, external micleus~orth7fun^uius''cun7atu 8 TTo' 

 ,. ,, i , nucleus of the funiculus gracilis (or clava) 771 funiculus 



termination OI a large number Of gracilis: # 2 . funiculus cuneatus; c.c., central canal; fa 



/o,i /a,2 external arciform fibres. 



nbres; most ot the cranial nerves 



find in it their origin, and in it the most diverse systems 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 Figs. 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 



DECUSSATION 

 (Landois.) 



OF THE PYRAMIDS. 



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

 n.XI, nucleus of the accessorius 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 I 



