THE CEREBRUM 



239 



Certain concentrically striated bodies, corpora amylacea, are 

 often found in the vicinity of the ventricles and along the olfac- 

 tory tract, as well as in other localities. After treatment with 

 iodine solution and sulphuric acid they* take a violet color, there- 

 fore resembling starch in their reactions hence their name. 



The arrangement of the layers of the gray matter is subject to 

 considerable modification in different parts of the cerebrum. As 

 in the spinal cord, the difficulties of tracing the course of the nerve- 



FIG. 155. PYRAMIDAL GANGLION-CELL AND NEUROGLIA-CELL FROM HUMAN CERE- 

 BRAL CORTEX PREPARED BY THE GOLGI METHOD. 



a. Axis-cylinder process of the ganglion-cell. 



fibers are increased by the numerous collaterals given off from the 

 axis -cylinder processes of the ganglion -cells. 



The paths followed by the fibers of the white matter are very 

 complicated. The tracts have been mapped out largely by prepa- 

 rations made by Weigert's method and its modifications. In gen- 

 eral these fibers may be divided into three groups: 



a. Projection fibers, which constitute the corona radiata, pass- 

 ing from the peduncles of the cerebrum and the basal ganglia to 

 the cortical gray matter. 



b. Association fibers, which bring parts of the same hemis- 

 phere into relation with one another. 



c. Commissural fibers, which connect the opposite hemispheres 

 through the corpus callosum and the anterior commissure. 



