406 NORMAL HISTOLOGY AND ORGANOGRAPHY. 



a few large pyramidal cells, and it is not well defined 

 from the preceding layer. There is present in this 

 layer: (i) multipolar cells with short neuraxes (Golgi 

 cells) whose dendrites project in all directions ; and 

 (2) cells with slightly branched dendrites and with 

 neuraxes passing toward the surface of the brain 

 where they terminate in the molecular outer layer. 

 The cells of this layer are triangular or spindle-shaped 

 and vary considerably in size. 



5. The medullary substance is composed of a mass 

 of nerve fibers that take a radial course and in which 

 we can detect no structural difference. Physio- 

 logically, however, we can divide them into four 

 classes as follows : i , projecting or centrifugal fibers 

 which indirectly connect the cerebral elements with 

 the periphery of the body; that is, they carry im- 

 pulses away from the nerve center; 2, commissural 

 fibers that connect corresponding parts of the two 

 cerebral hemispheres through the corpus callosum; 

 3, association fibers that connect different parts of 

 the same hemisphere ; 4, centripetal fibers or terminal 

 fibers, those that come from cell bodies in the same 

 or the opposite hemisphere, or in some more distant 

 nerve center, and that ultimately arborize about 

 nerve elements in the cerebral cortex. In a strict 

 sense the second and the third class fall under either 

 the centrifugal or the centripetal group. 



THE NEUROGLIA. 



The neuroglia tissue represents a special form of 

 supporting elements found exclusively in the central 

 nervous system and in the retina. It develops from 



