224 ELEMENTS OF MAMMALIAN ANATOMY 



The Cerebellum, or Little Brain.— The cerebellum, which in 

 the cat lies caudad of the cerebrum and dorsad of the medulla, 

 resembles the cerebrum in being composed of an outer layer of 

 gray matter or cells and an inner mass of white matter made up 

 of fibers. While within the cerebrum there are several impor- 

 tant ganglia or masses of gray matter, in the cerebellum only 

 one chief mass of gray matter, the corpus dcnlatum, is present 

 in each hemisphere. 



The outer layer of gray matter, known as the cortex, is folded 

 into numerous convolutions, between which are deep sulci 

 (Fig. io6). The central core of white matter forms an arbor- 

 escence known as the arbor vitce. 



The cerebellum (Fig. 103) is seen to consist externally of two 

 lateral portions, the cerebellar hemispheres, a median vermiform 

 process and three pairs of peduncles or crura which are bands 

 of fibers uniting it with other parts of the brain and cord 

 (Fig. 107) . The separation between the hemispheres and vermis 

 or vermiform process is most marked on the cranial aspect. 



The peduncles are named, according to their location, supe- 

 rior, middle, and inferior. The middle peduncle, or brachium 

 pontis, is a dorsal prolongation of the fibers of the pons Varolii 

 (Fig. 104). In order to display the other peduncles a portion of 

 the cerebellum must be cut or picked away with the forceps. 

 The superior one, known also as the brachium conjunctivum, ex- 

 tends as a cord of fibers along the cranial half of the fourth 

 ventricle and then beneath the corpus quadrigeminum. The 

 inferior peduncle, or restiform body, forms part of the boundary 

 of the caudal half of the fourth ventricle and enters the cere- 

 bellum between the other two peduncles. It is composed of 

 fibers from the spinal cord and medulla. 



LABORATORY STUDIES AND SUGGESTIONS 



1. Describe the meninges of the central nervous system. 



2. Which of the five parts of the brain are exposed dorsally? 



3. Draw the lateral aspect of the brain and label all features. 



4. Draw the ventral aspect of the brain and label all features. 



5. Draw the dorsal aspect of the brain after the dorsal portion, including 

 corpus callosum and fornix, has been removed. 



