CEREBELLUM. 345 



around the cell bodies of Purkinje's cells (Fig. 398). Often the basket 

 surrounds also the beginning of their neuraxons. 



The small cortical cells, distinguished from the basket cells since 

 their neuraxon are not in relation with Purkinje's cells, may be divided 

 into two types connected by intermediate forms. The cell bodies of the 

 first type are nearly or quite as large as those of the basket cells. Its 

 two to five dendrites lie in the sagittal plane like those of Purkinje's cells; 

 its slender neuraxon, i mm. long or more, sometimes forms loops, and 

 is characterized by abundant branches in its proximal part. The terminal 

 branches are few. The second type is in general somewhat smaller; the 

 shorter neuraxons of its cells branch in their immediate vicinity. The 

 elements of the first type form the bulk of the relatively numerous small 

 cortical cells, and are found throughout the gray stratum, though they are 

 more abundant in its superficial part. The second type appears every- 

 where in the gray stratum. 



The medullated nerve fibers found in the gray layer are prolongations 

 from the granular stratum. In part they proceed toward the surface 

 where, after losing their myelin, they end in branches among the dendrites 

 of Purkinje's cells; in part they run between the bodies of Purkinje's 

 cells lengthwise of the convolutions. 



The neuroglia of the cerebellum consists of short-rayed stellate cells 

 found in all the layers; of long-rayed cells found in the white substance; 

 and of peculiar cells with small bodies found at the outer boundary of the 

 granular layer. These send only a few short processes inward, but many 

 long processes straight out to the free surface, where they end in triangu- 

 lar expansions. In this way a thick peripheral neuroglia layer is produced. 



As long as the cerebellar cortex is not fully developed it presents a 

 series of peculiarities which are lacking in the adult. Thus in embryos 

 and young animals the partly developed gray stratum is covered by a 

 superficial granular layer, the cells of which later become nerve and neu- 

 roglia cells of the cortex. 



HEMISPHERES. 



The ascending fibers of the lemniscus and the descending cerebro- 

 spinal or pyramidal tracts, continue from the medulla through the pons and 

 peduncles of the cerebrum into the hemispheres. They enter them on 

 each side between the thalamus and the lentiform nucleus (a subdivision 

 of the corpus striatum) as seen in Fig. 401. The fibers of the ascending 

 tract have received accessions from the cerebral nerves, the thalamus, 

 corpora quadrigemina, and other special nuclei near which they pass. 

 Many of the fibers which arise in the gracile and cuneate nuclei terminate 



