THE NERVOUS SYSTEM. 



109 





rived (Fig. 324, n.g, n.c), and outside of the latter is an accessory nucleus 

 formed (Fig. 324, n.c'). Internally to these latter, and also derived from 

 the cells of the base of the posterior cornu and appearing in the floor of 

 the fourth ventricle, when the central canal opens are the nuclei of the 

 spinal accessory, vagus, and glosso-pharyngeal nerves. In the upper part 

 of the medulla also, to the outside of these three nuclei, is found the 

 principal auditory nucleus. All the above nuclei appear to be derived 

 from a continuation of the grey matter of the spinal cord, but a fresh col- 



-/<t. 



TL&T. 



FIG. 325. Section of the medulla oblongata at about the middle of the olivary body, f.l.a.., 

 anterior median fissure; n.a.r., nucleus arciformis; p, pyramid; XII. , bundle of hypoglossal nerve 

 emerging from the surface; at 6, it is seen coursing between the pyramid and the olivary nucleus, 

 o.; f.a.e., external arciform fibres; n.I., nucleus lateralis; a, arciform fibres passing toward resti- 

 form body, partly through the substantia gelatinosa, g., partly superficial to the ascending root of 

 the fifth nerve. a.V.; X, bundle of vagus root emerging; />., formatio reticularis; c.r., corpus resti- 

 forme, beginning to be formed, chiefly by arciform fibres, superficial and deep; n.c.. nucleus cunea- 

 tus; ii.o., nucleus gracilis; t., attachment of the ligula; f.s., funiculus solitarius; n.X., nX'., two 

 parts of the vagus nucleus ; n.XIL, hypoglossal nucleus; n.t., nucleus of the funiculus teres: n.am., 

 nucleus ambiguous; r., raphe; A., continuation of the anterior column of cord; o'. o"., accessory 

 olivary nucleus; P.O., pedunculus olivae. (Schwalbe.) (.Modified from Quain.) 



lection of grey matter not represented is interpolated between the anterior 

 pyramids and the lateral column, contained within the olivary promi- 

 nence, the wavy line of which (corpus dentatum) is doubled upon itself 

 at tin angle with the extremities directed upward and inward (Fig. 325, o). 

 There may also be a smaller collection of grey matter on the outer and 

 inner side of the olivary nucleus known as accessory olivary nuclei. 



FUNCTIONS OF THE MEDULLA OBLONGATA. 



The functions of the medulla oblongata, like those of the spinal cord, 

 may be considered under the heads of: 1. Conduction; 2. Transference 

 and Reflection; and, in addition, 3. Automatism. 



1. In conducting impressions the medulla oblongata has a wider ex- 

 tent of function than any other part of the nervous system, since it is 



