118 ANTHROPOLOGY. 



or semilunar. The two former are connected by the tortuous transverse 

 laminae of the superior vermiform process, and the two posterior by those 

 forming the floor of the posterior notch, d. The median portion presents 

 the single or azygos superior median lobe or vermiform process, e. The 

 interior surface of each hemisphere presents five lobes. Most anterior and 

 distinct from the hemisphere are : first, the flocculus or pneumogastric lobule, 

 connected to its fellow and to the nodule by the inferior medullary velum ; 

 second, the tonsilic lobe or amygdalar, on the side of the ventricle, and con- 

 nected to the opposite through the uvula or spigot ; third, the digastric ; 

 fourth, the gracilis ; fifth, the semilunar, which is joined to its fellow by the 

 convex transverse laminae at the bottom of the posterior notch ; sixth, the 

 inferior median lobe, or vermiform process, presents from before backwards 

 three lobules ; the nobule most anterior, next the uvula or spigot, and 

 posteriorly the pyramid. 



The fourth veyitride is a lozenge-shaped cavity, situated in the upper and 

 posterior part of the medulla oblongata, and formed by the separation of its 

 postero-lateral columns (corpora restiformia). The cerebellum contributes 

 to inclose it by means of the anterior laminae of the superior vermiform 

 process and the valve of Yieussens, and below and behind by the inferior 

 vermiform process. 



5. Medulla Oblongata. The medulla oblongata, or spinal bulb, is that 

 conical portion of white substance which extends from the lower margin of 

 the pons Varolii to the spinal cord, on a level Avith the ring of the atlas. 

 Its upper end or base, though apparently limited by the pons, is prolonged 

 upwards through it to the crus cerebri of each side. Inferiorly, there is no 

 distinction between it and the spinal cord posteriorly or laterally. It pre- 

 .sents an anterior and posterior median fissure, which divides it into two 

 sj^mmetrical portions, each of which is marked by three grooves and four 

 convex eminences, viz. the anterior pyramid, the corpora olivaria, the cor- 

 pora restiformia, and the posterior pyramid. 



The posterior fissure is continuous with that of the spinal cord. It is 

 narrow, deep, and lined by the pia mater. The anterior fissure^ the con- 

 tinuation of the spinal, is broader but shallower, and lined by transverse 

 «•ommissural fibres. Nearly an inch below the pons this fissure is inter- 

 rupted by the decussating fasciculi^ three or four in number, which ascend 

 obliquely inwards from the lower end of each pyramid to the opposite one, 

 interlacing or interdigitating with each other. 



The anterior pyramids are two narrow, convex, white bands, about an 

 inch long, small inferiorly, and partially united by the decussating fasciculi. 

 They appear to be the direct as well as decussating medium of communi- 

 cation between the anterior fibres of the cord, the mesocephalon, crura 

 cerebri, corpora striata, and cerebral hemispheres. 



The corpora olivaria are smaller and shorter than the pyramids, are 

 external and posterior to these, and separated by a groove both from them 

 and from the restiformia. They only exist in man and quadrumana. 

 White and fibrous externally, when divided they present a mass of grey 

 neurine called olivary ganglion or corpus dentatum. 

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