THE BRAIN. 



489 



situated, connecting the middle peduncles of the cerebellum. 

 Among its fibers are collections of gray matter. 



Functions of the Pons Varolii. The anatomic relations of the 

 pons show that it must serve as a conductor of impulses both to 

 and from the centers above. As to the function of its gray matter, 

 comparatively little is known, save that from a portion of it some 

 of the cranial nerves arise. If it is stimulated or divided, pain 

 and spasms are produced. When a lesion is situated in the lower 

 half of the pons, there result facial paralysis on the same side as 

 the lesion, and motor and sensory paralysis on the opposite side 

 of the body. This is called alternate paralysis. If the lesion is 

 in the upper half of the pons, the facial paralysis and that of the 

 body are on the same side. When the pons is suddenly and ex- 

 tensively injured, a condition of hyperpyrexia is often produced, 

 the temperature rising rapidly within an hour. This is probably 



M)endrite. 



Blood-vessel. -V 



^ : - ' -f- r ..- c .- ? -o^ . Nerve-fiber 



^ layer. 



4; -~*-"" "-i- j 



FIG. 280. Section through the human cerebellar cortex vertical to the surface of 

 the convolution; treatment with Miiller's fluid; x 115 (Bohrn and Davidoff). 



due to the influence of the gray matter in the floor of the fourth 

 ventricle, or possibly to the involvement of some special heat- 

 regulating center. 



