Quain's elements of anatomy . ind the pyi-amid. The root-bundles of the hypoglossalnerves generally pass between them and the chief olivary nucleus after traversingthe olivary peduncle, but sometimes the nerve pierces the chief nucleus near itsmesial edge. Other small collections of grey matter and nerve-cells are scattered incertain parts of the formatio reticularis, as well as one or two distincttracts in connection with the external arcuate fibres, and a considerableamount in the median septum or raphe. These three structmes maytherefore next be described. 296 THE MEDULLA OBLONGATA. The for
Quain's elements of anatomy . ind the pyi-amid. The root-bundles of the hypoglossalnerves generally pass between them and the chief olivary nucleus after traversingthe olivary peduncle, but sometimes the nerve pierces the chief nucleus near itsmesial edge. Other small collections of grey matter and nerve-cells are scattered incertain parts of the formatio reticularis, as well as one or two distincttracts in connection with the external arcuate fibres, and a considerableamount in the median septum or raphe. These three structmes maytherefore next be described. 296 THE MEDULLA OBLONGATA. The formatio reticularis (figs. 267, 268,/.r.) occupies the whole ofthe anterior and lateral areas of the medulla, dorsal to the pyramids andolives respectively. It is thus named on account of the appearance whichit presents in a transverse section viewed under a moderate magnifyingpower (fig. 270), This reticular appearance is caused by the intersec-tion of bundles of fibres belonging to two sets which run at right angles Fig. rff. XII. Fig. 270,—Part op the reticular formation of the medulla oblongata (Henle). ??. a., reticiilaris alba ; , reticularis grisea; between them a root-bundle of thehypoglossus (XII). The longitudinal fibres of the reticular formation are cut across ;the transversely coursing fibres are internal arcuate fibres, passing on the right of thefigure towards the raphe. to one another. Those of the one set are longitudinal, and these areintersected by transverse fibres, which pass obliquely from the rapheoutwards and somewhat backwards with a curved course towards thefuniculus gTacilis and funiculus cuneatus, and the olivary nucleus ; andalso in the upper part of the mediiUa, towards the restiform body. In some parts grey matter with nerve-cells enters into the constitutionof the formatio reticularis. The cells are especially large and numerousin the reticular formation of the lateral area near the remains of theanterior cornu; and its grey matter is p
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