PHYSIOLOGICAL ANATOMY OF THE BULB 6oi 



the gray substance of the lateral halves. Commissural fibres also con- 

 nect the gray matter of the lateral tracts with the corpora dentata of 

 the olivary bodies, and the olivary bodies with the cerebellum, their 

 fibres forming part of the inferior peduncles of the cerebellum. In 

 addition, it is probable that fibres, taking their origin from all the gray 

 nodules of the bulb, pass to the parts of the encephalon situated above. 



So far as the fibres of origin of the cranial nerves are concerned, it 

 may be stated in general terms that a number of the motor roots arise 

 from the gray matter of the floor of the fourth ventricle, the roots of 

 sensory nerves arising from gray nuclei in the posterior portions. 



It is hardly necessary to discuss the action of the bulb as a con- 

 ductor of sensory impressions and of motor stimulus to and from the 

 brain. It is evident that there is conduction of this kind from the spinal 

 cord to the ganglia of the encephalon, and this must take place through 

 the medulla : a fact which is inevitable, from its anatomical relations, 

 and which is demonstrated by its section in living animals. 



The action of the bulb as a reflex nerve-centre depends on its gray 

 matter. When the gray substance is destroyed, certain important reflex 

 phenomena are instantly abolished. From its connection with the 

 cranial nerves, one would expect it to play an important part in the 

 movements of the face, in deglutition, in the action of the heart and of 

 various glands, important points that are fully considered under ap- 

 propriate heads. 



The connections of the bulb with the different columns of the cord 

 are as follows : 



The columns of Tiirck pass directly from the cord to the cerebrum 

 by fibres at the outer borders of the anterior pyramids. 



The crossed pyramidal tracts pass to the anterior pyramids and 

 there decussate. 



The anterior ground columns and the lateral bundles connect the 

 gray matter of the cord with the gray matter of the bulb. 



The direct cerebellar fasciculi and the columns of Goll pass to the 

 cerebellum through the funiculi graciles, next the posterior fissure. 



The columns of Burdach and the descending and ascending cerebel- 

 lar tracts pass to the restiform bodies. 



The fibres of the funiculi graciles and some of the fibres of the col- 

 umns of Burdach go to the cerebellum without decussating. A few 

 fibres of the restiform bodies go directly to the cerebrum. 



Newe-centres in the Bulb. The following centres have been 

 located in the bulb : 



i. The centre for closure of the eyelids is related to the nuclei of 

 origin of the facial and the trifacial. 



