482 TEXT-BOOK OF PHYSIOLOGY. 



concerned in the transference of the food from the mouth to 

 the stomach. (See page 175.) 



6. An articulation center, which coordinates the muscles necessary to 

 the production of articulate speech. 



In addition, the gray matter contains centers which influence the 

 secretion of saliva, provoke vomiting, coordinate the muscles of the 

 face concerned in expression, and control the secretion of the per- 

 spiration. 



As conducting pathways. The anterior pyramids of the medulla 

 and their continuations through the more ventral portions of the 

 pons, being portions of the general pyramidal tract, serve to conduct 

 volitional efferent nerve impulses from higher portions of the brain 

 to the spinal cord. Division of either of these pathways is at once 

 followed by a loss of volitional control of the muscles below the 

 section. 



The dorsal or tegmental portion, containing the fillet and Gowers' 

 tract, serves to transmit afferent nerve impulses from the spinal 

 cord to higher portions of the brain. Transverse division of one-half 

 of the dorsal portion of the pons is followed by complete anesthesia 

 of the opposite half of the body without any impairment of motion. 



The restiform bodies constitute a pathway between the spinal cord 

 and the cerebellum. The transverse fibers of the pons associate 

 opposite but corresponding portions of the cerebellar hemispheres. 



The Crura Cerebri. The crura cerebri consist ventrally of fibers 

 which are largely derived from the pyramidal tracts and are con- 

 tinuous with the longitudinal fibers of the ventral portion of the pons 

 and medulla; and dorsally of fibers continuous with those coming 

 through the lower portions of the tegmentum. Hence they are con- 

 ductors of motor impulses in the former and of sensor impulses 

 in the latter region. It is not definitely known as to whether reflex 

 actions take place through the gray matter, the locus niger, or not. 



The gray matter beneath the aqueduct of Sylvius contains nerve- 

 cell groups which are centers for reflex actions in connection with 

 ocular movements: e. g., closure of the lids, contraction of the sphinc- 

 ter pupillae, convergence of the eyes, etc. 



The Corpora Quadrigemina. From the anatomic relation of 

 the anterior quadrigeminal body (the pregeminum) to the optic tract, 

 on the one hand, and to the optic radiation, on the other, the in- 

 ference can be drawn that it is in some way essential to the per- 

 formance of the visual process. Experimental investigations and 

 pathologic changes support the inference. 



Irritation of the pregeminum in monkeys on one side is followed 

 by dilatation of the pupils first on the opposite side and then almost 

 immediately on the same side. The eyes at the same time are also 

 widely opened and the eyeballs turned upward and to the opposite 



