

THE CENTRAL NERVOUS SYSTEM. 69 



The reflexes which are carried out through the medulla oblongata 

 are those concerned with the secretion of saliva and of the gastric and 

 pancreatic juices; with the movements of the oesophagus, stomach, 

 and intestine, including those involved in vomiting ; with the regula- 

 tion of the heart and blood-vessels ; and with the regulation of 

 respiration. 



The physiological conducting paths in the medulla oblongata are 

 (1) the motor path formed by the pyramid; (2) the rubro-spinal tract, 

 lying dorsal to (4) ; (3) the chief sensory path, consisting of (a) the 

 funiculus gracilis and funiculus cuneatus continued upwards from the 

 spinal cord, (b) the cell stations in the nucleus gracilis and nucleus 

 cuneatus, (c) the sensory decussation, and (d) the fillet, in which are 

 also included the spino-thalamic fibres which have already crossed in 

 the spinal cord ; (4) the antero-lateral ascending tract, running upwards 

 just behind the olivary nucleus ; (5) the direct cerebellar tract running 

 into the restiform body of its own side ; (6) the vestibulo-spinal path, 

 or posterior longitudinal bundle (medial longitudinal fasciculus), which 

 lies in the formatio reticularis behind the fillet, and is concerned with 

 the function of equilibration, connecting Deiters' nucleus and the nuclei 

 of the third, fourth, and sixth cranial -nerves with the spinal cord ; 

 (7) the spino-tectal fibres, which run upwards, forming part of the 

 antero-lateral ascending tract. 



THE PONS. 



The outstanding feature of the structure of the pons is the 

 presence of a large number of decussating nerve fibres, which pass back- 

 wards on each side to form the middle peduncles of the cerebellum. 

 These transverse fibres occupy the ventral part of the pons, and 

 split up the pyramid into a number of separate bundles (fig. 19). 

 Behind them are the fillet and the fornjatio reticularis with the con- 

 ducting paths described in connection with the medulla oblongata, 

 these paths occupying much the same relative positions as they do in 

 the medulla. 



Lying posteriorly in the upper part of the fourth ventricle, and in 

 or near the floor of the ventricle, are found the nuclei of the fifth, sixth, 

 seventh, and eighth nerves. The upward continuation of the nucleus 

 ambiguus forms the motor nuclei of the fifth and seventh nerves. The 

 sixth nucleus, also motor, lies close to the floor of the fourth ventricle 

 and near the motor nucleus of the facial. The sensory nucleus of the 

 fifth nerve, lying laterally to the motor nucleus, receives some of the 

 sensory fibres of this nerve. The other sensory fibres of the fifth 



