406 CEREBELLUM. 



hemispheres below. The superior and inferior vermiform 

 processes, though distinguished by different names ; are 

 regarded as essentially one and the same lobe, as they 

 are continuous, the one with the other, and have been 

 called the median lobe, or primitive lobe of the cerebel- 

 lum. 



This primitive lobe is found to be the only portion present 

 in fish and reptiles, while in birds the hemispheres consist 

 simply of small lateral offsets from this central fundamental 

 part. 



Upon the inferior vermiform process, three little emi- 

 nences have received names, the most anterior being called 

 the nodule; the middle, the uvula; and the posterior, the 

 pyramid. 



. FIG. 114. The cerebellum consists of 



cineritious, or gray matter 

 externally, and white or 

 medullary internally. In 

 making a horizontal section, 

 a large white central me- 

 dullary mass is seen, which 

 can be traced from the one 

 hemisphere to the other. In 

 a vertical section, a beauti- 

 ful arrangement of the med- 

 ullary striae, resembling the branches of a tree, is seen, and 

 hence called arbor vitce. If the vertical incision be made upon 

 the outer third of the hemisphere, there will be noticed in the 

 interior of the white central ma$s, a small yellowish or gray 



FIG. 114 represents the arbor-vita of the cerebellum, a Tubercula quadri- 

 gemina. 6 Superior surface of the cerebellum, c Inferior surface and arbor 

 vitee ; from the trunk of this latter three fasciculi are traced to the tubercula 

 quadrigemina, the most internal of these fasciculi is, d A fibrous layer ; on the 

 outside of this is, e The next fasciculus, and on the outside of this again is, 

 /The third fasciculus, g A thin medullary layer passing from the crus cerebelli 

 to the cerebrum, h Anterior extremity of fourth ventricle, i Middle furrow on 

 the floor of fourth ventricle, j Tracts of nervous matter leading to the audito- 

 ry nerve, k Nervous matter presenting a raised appearance on the floor of 

 fourth ventricle. I Middle fissure in calamus scriptorius. m Corpora-restifor- 

 mia. n A side view of the spinal marrow. 



