30 CONSIDERATIONS OF THE BRAIN OR ENCEPHALON. 



characterized by its parallel crescentic sulci, which give it a strati- 

 fied appearance. It shows a partial subdivision into lateral 

 hemispheres produced by a posterior median depression, called 

 the posterior cerebellar notch, and by a longitudinal groove on its 

 inferior surface, called the vallecula cerebelli. The vallecula' is 

 fitted over the posterior surface of the medulla. The cerebellum 

 is, therefore, separated from the medulla oblongata by a sharply 



Fig. 17. Diagrammatic horizontal section of vertebrate brain. 

 (Morris's Anatomy after Huxley.') 



a. Metencephalon. b. Thalamus. c. Medulla oblongata. d. Cerebellum, e. Lateral ven- 

 tricle, f. Olfactory diverticulum. g. Lamina terminalis. h. Corpus striatum. i. Mid-brain. 

 j. Pineal body. k. Interventricular foramen. 



curved, rainbow-shaped fissure. That fissure is the transverse 

 fissure of the cerebellum (fissura Iransversa cerebelli) which, as 

 already pointed out, is bridged over by the arachnoid and con- 

 tains the cisterna cerebello-medullaris. 



Inferior View. The base of the brain presents three areas, 

 situated in three successive levels, which correspond in location 

 and extent to the great fossae in the base of the cranium (Figs. 21 

 and 27). The anterior area, situated in the anterior cranial fossa, 

 occupies the highest level; the middle area is intermediate in 

 position; it occupies the middle fossa and together with the anterior 

 area comprises all of the base of the cerebrum which is visible in 

 the complete brain; and, the posterior area, which is but the base 

 of the rhombencephalon, is situated at the lowest level in the 

 posterior fossa of the cranium. 



The anterior area of the base of the brain is divided into 

 lateral halves by the longitudinal fissure of the cerebrum, and 



