256 THE NERVOUS SYSTEM 



later that the integrity of the cerebrum is essential to any 

 intellectual operation, and manifestly, under the conditions 

 mentioned, there can be no voluntary motion which indi- 

 cates any degree of intelligence; but the fact remains that 

 the animal can perform movements which are different from 

 the reflex movements depending on the presence of the cord 

 when all other parts of the cerebro-spinal axis have been 

 removed. The pons is apparently "an organ capable of 

 originating impulses giving rise to voluntary movements, 

 when the cerebrum, corpora striata and optic thalami have 

 been removed, and it probably regulates the automatic vol- 

 untary movements of station and progression." (Flint.) 



Nor can it be doubted that an animal thus mutilated feels 

 pain. It is probable that the sensory impression is received 

 by some of the gray centers in the pons itself, but not being 

 conveyed to the cerebrum, is not remembered. 



The Crura Cerebri, Corpora Striata, Optic Thalami, Inter- 

 nal Capsule and Corpora Quadrigemina. 



It will be well before discussing the cerebrum to consider 

 briefly other collections of gray and white matter in the 

 neighborhood of the upper part of the pons. 



The crura cerebri, passing upward from the anterior part 

 of the pons, diverge to run apparently underneath the cor- 

 pora striata and optic thalami iri the direction of the cere- 

 bral hemispheres. They are about % mcn l n g an d slightly 

 broader above than below. The main bulk of each crus con- 

 sists of white fibers, but a collection of gray matter (locus 

 niger) divides the band into a lower or superficial section, 

 called the crusta, and an upper or deep section, called the 

 .tegmentum. There is also some gray matter in the tegmen- 

 tum proper. The fibers of the tegmentum are supposed to 

 convey afferent impressions chiefly, and end for the most 

 part in the optic thalamus, though some are continued to the 

 cerebrum through the internal capsule. The fibers of the 



