422 



THE CENTRAL NERVOUS SYSTEM. 



cells (granular cells). This layer also contains the stellate ganglion 

 cells. The latter are not numerous, but lie scattered, and each pos- 

 sesses several short dendrites and a peripherally directed neuraxis 

 which ends in the molecular layer in a rich arborization. The deep 

 nerve-fibers are grouped into bundles which inclose between them 

 the granular and stellate cells just mentioned. These nerve-fibers 



Mitral cells. 



Molecu- 

 lar layer. 



Layer of olfactory 

 glomeruli. 



Peripheral nerve 

 fibers. 



Fig. 337. The olfactory bulb, after Golgi and Ram6n y Cajal. 



not shown. 



The granular layer is 



are derived partly from the neuraxes of the pyramidal or mitral cells 

 and partly from the cells of the molecular layer, while some of 

 them are centripetal fibers from the periphery, which end between 

 the granules of the fifth layer. 



E. EPIPHYSIS AND HYPOPHYSIS. 



In mammalia the epiphysis, or pineal gland, consists of a 

 fibrous capsule derived from the pia mater, from which numerous 

 fibrous tissue septa and processes pass into the gland, uniting to 

 form quite regular round or oval compartments in which closed 

 follicles or alveoli, whose walls consist of epithelial cells, are found. 

 In the lower portion of the epiphysis there is found a relatively large 

 amount of neuroglia tissue, consisting of coarse fibers, as has been 

 shown by Weigert. The epithelial cells forming the walls of the 

 follicles are of cubic or short columnar shape, and may be arranged 

 in a single layer or may be pseudostratified or stratified. Follicles 



