THE BRAIN. 509 



without fotmdation. It has now heen clearly demonstrated 

 that the lower region of the spinal cord is, in the dog and prob- 

 ably most mammals, the part of the nerve-centers essential for 

 the sexual processes. 



Crura Cerebri and Pons Varolii.— As has been already noted, 

 the peduncles (crura) are the paths of impulses from certain 

 parts of the cerebral cortex, the basal ganglia, and the spinal 

 cord. The functions of the gray matter of the crura are un- 

 known. But, since forced movements ensue on unilateral sec- 

 tion, it is plain that they also have to do with muscular co- 

 ordination. 



The transverse fibers of the pons Varolii connect the two 

 halves of the cerebellum. Its longitudinal fibers have extensive 

 connections — the anterior pyramids and olivary bodies of the 

 medulla, the lateral, and perhaps also a part of the posterior 

 columns of the cord, while upward these fibers connect with 

 the crura cerebri and so with the cortex. 



FathologicaL — Paralysis of the face usually occurs on the 

 same side as that of the rest of the body ; hence it raust be 

 inferred that there is a decussation somewhere of the fibers of 

 the facial nerve*; but there is much still to be learned about 

 this subject. 



Medulla Oblongata, — In some animals (frogs) it is certainly 

 known that this region of the brain has a co-ordinating func- 

 tion, and it is probable that it is concerned with such uses in 

 all animals that possess the organ, or rather collection of organs, 

 seeing that this part of the brain must be regarded as especially 

 a mass of centers, the functions of which have been already 

 considered at length. So long as the medulla is intact, life may 

 continue ; but, except under special circumstances, which do 

 not invalidate this general statement, its destruction is followed 

 by the death of the animal. 



We may simply enumerate the centers that are usually 

 located in the medulla : The respiratory (and convulsive), car- 

 dio-inhibitory, vaso-motor, center for deglutition, center for 

 the movements of the gullet, stomach, etc., and the vomiting 

 center ; center for the secretion of saliva and possibly other of 

 the digestive fluids. Some add a diabetic and other centers. 



