GANGLIA OF THE CEREBKUM. 



465 



matter, are the subslantia nigra of the crus cerebri, the commissura 

 mollis, the floor of the third ventricle immediately behind and beneath 



Fig. 309. 



Diagram of the mutual relations of the principal encephalic centres, as shown in a vertical sec- 

 tion. A. Cerebrum. B. Cerebellum, c. Sensori-motor tract, including the olfactory ganglion (olf), 

 the tubercula quadrigemina, or optic ganglia (opt), and the auditory (aud), with the thalami optici 

 (thai) and the corpora striata (cs). D. Medulla oblongata. E. Spinal cord ; a, olfactory nerve ; 

 6, optic ; c, auditory ; d , pneumogastric ; e, hypoglossal ; /, spinal accessory. Fibres of the medullary 

 substance of the cerebrum are shown connecting its ganglionic surface with the sensori-motor tract. 



the anterior commissure, and the tuber cinereum. The pineal body 

 contains pale rounded apolar cells and scattered nerve-fibres, and 

 generally also a considerable quantity of sabulous matter (princi- 

 pally carbonate of lime, with phosphate of lime and magnesia). 

 The pituitary body contains in its anterior reddish lobe no nervous 

 elements at all, but the "elementary tissues of blood-vascular 

 glands." (EcJcer.) The posterior smaller lobe consists of a fine 

 granular substance with nuclei and bloodvessels; and also fine 

 varicose nerve-fibres, which, like the vessels, descend from the in- 

 fundibulum. 



4. The Cerebral Hemispheres. 



The white substance of the hemispheres of the brain consists en- 

 tirely of nerve-fibres, ^fa^ to ^^ of an inch (average g ^ of 

 an inch) in diameter. These never form plexiform interlacements 

 30 



