Motor 

 or 



MEDULLA OBLONGATA. 129 



2. A centre reflecting impressions which influence the secretion of saliva. 

 (See page 28.) 



3. A centre for sucking, mastication and deglutition, whence are derived 

 motor stimuli exciting to action and coordinating the muscles of the palate, 

 pharynx and oesophagus, necessary for the swallowing of the food. The 

 secretion of saliva is also controlled by a centre in the medulla. 



NERVOUS CIRCLE OF DEGLUTITION. (2d and 3d Stages.) 



Excitor (" Palatal branch of 5th pair. 



or Pharyngeal branches of the glosso pharyngeal. 



Centripetal Superior laryngeal branches of the pneumogastric. 



Nerves. [ (Esophageal branches of the pneumogastric. 



Pharyngeal branches of the pneumogastric, derived 



from the spinal accessory. 



Hypoglossal and branches of the cervical plexus. 

 Centrifugal Inferior or recurrent laryngeal. 



Nerves. Motor filaments of the 3d division of the 5th pair. 



Portio dura. 



4. A centre which coordinates the muscles concerned in the act ot 

 vomiting. 



5. A Speech centre, coordinating the various muscles necessary for the 

 accomplishment of articulation through the hypoglossal, facial nerves and 

 the 2d division of the 5th pair. 



6. A centre for the harmonization of muscles concerned in expression, 

 reflecting its impulses through the facial nerve. 



7. A Cardiac centre, which exerts (i) an accelerating influence over the 

 heart's pulsations through accelerating nerve fibres emerging from the cer- 

 vical portion of the cord, entering the inferior cervical ganglion, and thence 

 passing to the heart; (2) an inhibitory or retarding influence upon the action 

 of the heart, through fibres of the spinal accessory nerve running in the 

 trunk of the pneumogastric. The cardio-inhibitory centre is in a state of 

 tonic excitement and continuously sending impulses to the heart which 

 exert an inhibitory influence upon its action. It may be stimulated directly 

 by ancemia as well as venous hyperaetniaof the blood vessels of the medulla 

 and increased venosity of the blood. It is excited reflexly by the stimula- 

 tion of the central end of the vagus, sciatic and splanchnic nerves. 



8. A Vasomotor centre, which by alternately contracting and dilating 

 the blood vessels through nerves distributed in their walls, regulates the 

 quantity of blood distributed to an organ or tissue, and thus influences 

 nutrition, secretion and calorification. The vasomotor centre is situated in 

 the medulla oblongata and pons Varolii, between the corpora quadrigemina 



