76 THE NERVOUS SYSTEM 



glandular) impulses may pass from the gray nuclei of the organ to many 

 parts of the body besides the head by way of the closely connected 

 medulla below and the internal capsule above. 



The Medulla Oblongata. The medulla oblongata, or bulb, as it is 

 sometimes called, is understood as compared with the nuclei just above 

 it on the base of the brain, though the actual details of the structure and 

 functions of the medulla are, however, not well known. In general, the 

 medulla is largely a conducting organ, with many small, but important 

 "centers" (neuronal regions) scattered in the interior of its 8 or 9 c.c. 

 It gives rise to seven or eight of the twelve so-called cranial nerves 

 (page 88). 



The white matter of the medulla is arranged in four bundles or columns 

 namely, the anterior pyramid, the lateral tract, the restiform body, 

 and the posterior pyramid on each side. 



The anterior pyramid is composed of fibers extending upward from the 

 direct pyramidal tract of the spinal cord and from the crossed pyramidal 

 tract. Some of these continue upward into the crus of the cerebrum, 

 others are lost in the pons, while still others pass to the cerebellum as part 

 of the restiform bundle. In a similar way the lateral tract, continuous 

 below with the lateral column of the cord, divides itself between the 

 cerebellum and the cerebrum, joining partly with the anterior pyramid. 

 The restiform body is made up largely of fibers from part of the posterior 

 column below, and having received fibers within the medulla in a com- 

 plex way, divides, part going to the cerebellum, and part upward farther 

 into the hemisphere. The posterior pyramid comes upward also from the 

 posterior column of the cord (GolPs column) and with a portion of the 

 preceding continues into the cerebrum as part of the fasciculi teretes. 

 Near the broad upper end of the medulla is the olivary body, containing 

 the gray nucleus called the corpus dentatum, and conspicuous ventrally 

 (anteriorly) on the medulla's surface. Fibers from this gray matter join 

 with part of the anterior column to form the olivary bundle ascending 

 into the crus of the hemisphere. 



The gray matter of the medulla, situated largely beneath (i. e., ventral 

 or anterior to the floor of the fourth ventricle), performs two general 

 functions. It is concerned with the cranial nerves (which will be mentioned 

 later see page 88), as already noted, and (as nuclei) with important 

 reflex activities. It is because the medulla connects and coordinates 

 these two important systems of nerves (those of special sense and motion 

 with those of the great reflex vegetative movements of the body), that 

 this portion of the spinal cord is of such unexcelled usefulness in the 

 organism. It is from the medulla more than from any other part of the 

 nerve-scheme that the vital functions are controlled and made to work 

 together, thus insuring the inherent unity of the individual animal. 

 Such basal functions as respiration, nutrition, circulation, and thermo- 

 taxis depend directly on the duties of the medulla. Here are controlled 

 the many varied secretions and movements of the whole complex alimen- 

 tary canal, the heart's action, the distribution of blood, the adapted move- 



