THE STRUCTURE OF THE MEDULLA OBLONGATA 



141 



them the name "tractus cerebello-tegmentalis bulbi," and believes that they descend from 

 the cerebellum by way of the restiform body, then arch ventrally over the surface of the 

 medulla, penetrate the pyramid or the anterior median fissure, and end in the reticular 

 formation of the opposite side (Fig. 153). According to Van Gehuchten (1904) some of the 

 ventral external arcuate fibers arise from cells in the reticular formation of the same and the 

 opposite side, and run through the restiform body to the cerebellum. 



Olivary Nuclei. The oval prominence in the lateral area of the medulla, 

 known as the olive, is produced by the presence just beneath the surface of a 

 large gray mass, the inferior olivary nucleus, with which there are associated 



Fig. 102. Diagram to illustrate the structure of the inferior olivary nucleus. (Cajal, Edinger.) 



two accessory olivary nuclei. The inferior olivary nucleus is very conspicuous 

 in the sections of this part of the medulla (Fig. 101). It appears as a broad, 

 irregularly folded band of gray matter, curved in such a way as to enclose a 

 white core, which extends into the nucleus from the medial side through an 

 opening, known as the hilus. Considered as a whole this nucleus resembles a 

 crumpled leather purse, with an opening, the hilus, directed medially. Sec- 

 tions at either end of the nucleus do not include this Opening, and at these 

 points the central core of white matter is completely surrounded by the gray 

 lamina. The fibers which stream in and out of the hilus constitute the olivary 



