256 THE RHOMBENCEPHALON. 



are continued into the hemispheres, the sulcus valleculas not cut- 

 ting them off. A bifurcated lamina of the arbor vitae enters into 

 the tuber. The horizontal sulcus separates it from the folium 

 vermis of the superior worm. The slender and inferior semilunar 

 lobules comprise the posterior two-thirds of the inferior surface 

 of each hemisphere, extending from the biventral lobule to the 

 postero-lateral border. Twelve to fifteen gyri compose the lob- 

 ules. The gyri are divided into three groups by the midgracile 

 and postgracile sulci; the anterior and middle groups are named 

 the anterior slender and posterior slender lobules, they constitute 

 the lobulus gracilis. The posterior is the inferior semilunar lobule. 

 The inferior semilunar lobule, only, is continuous with the gyri 

 of the vermis. The great size of the inferior and superior semi- 

 lunar lobules is the most characteristic feature of the human cere- 

 bellum. 



The gray matter of the cerebellum is composed of cortex 

 which covers the cerebellar laminae and of ganglia imbedded in 

 the medullary body (Figs. 81 and 84). 



I. CORTICAL GRAY MATTER. 



The cortex of the cerebellum (substantia corticalis cerebelli) 

 is made up of two thick layers visible to the naked eye, viz,, (i) 

 a superficial layer, and (2) a deep, granular layer. At the junc- 

 tion of these two layers is a single row of large pitcher-shaped cell- 

 bodies, which are characteristic of the cerebellar cortex and are 

 often visible to the unaided eye. They are the bodies of Purk- 

 inje's cells, and are considered in the deep part of the first macro- 

 scopic layer, where they form the stratum gangliosum. Under 

 the microscope three layers are easily seen, viz., (i) the gray layer 

 (stratum cinereum); (2) the ganglion cell layer (stratum gan- 

 gliosum); and (3) the granular layer (stratum granulosum). 



(i) Superficial Layer (Figs. 82 and 83). Thickest on the 

 laminae and thinnest beneath the fissures, this layer contains 

 small and large stellate cell-bodies with their processes, which 

 constitute the stratum cinereum proper; and the large Purkinje 

 cell-bodies with their dendrites and recurrent axones, together 



