104 PHYSIOLOGY. 



tion of connecting the different segments of the cord with each other. 

 By Mr. Solly they are regarded as the ganglia of the sense of hearing. 



The medulla oblongata has the general properties of the spinal 

 cord. It has the same property of reflection^ indeed in a higher de- 

 gree than any other part of the nervous system ; and the nerves 

 which arise from it are more prone than any others to reflex action. 

 It belongs also to the motor apparatus, and no other p5^ has so 

 great an influence on the production of motion, irritation of it exciting 

 convulsions in the whole trunk. The most important motory influ- 

 ences of the medulla oblongata, however, are those that subserve 

 respiratio?i and deglutition^ both of which, respiration more espe- 

 cially, depend upon it. All the rhythmical motions of respiration, 

 such as laughing, yawning, sighing, &c., depend upon it. The 

 faculty of the power of volition seems also to have its probable seat 

 in the medulla oblongata, according to some physiologists, for many 

 animals, after complete removal of the brain and cerebellum, still 

 retain the power of performing voluntary motions. (Flourens.) It is 

 doubtful how far the medulla oblongata participates in sensation, (as 

 alleged by Desmoulins, Magendie, Flourens.) Any conclusion in 

 this direction from experiments must be unsatisfactory, inasmuch as 

 all the phenomena that have been noted are readily referred to reflex 

 actions. 



All the psychological excitements or faculties, — affections, pas- 

 sion*,, &c., are realised, or made manifest by means of the medulla 

 oblongata ; and in those diseases which mental emotion is apt to give 

 rise to, many of the symptoms are referable to affections of the 

 medulla oblongata. 



The chief excitor nerve of the respiratory movements, is the affe- 

 rent portion of the par vagum ; the afferent portion of the fifth is, also 

 a powerful excitor. The chief motor nerves are the phrenic and in- 

 tercostals, which probably originate in the medulla oblongata, 

 though they issue from the cord at a point lower down. Several 

 other spinal nerves are concerned in the motor portion of the respi- 

 ratory process, as are also the facial nerve, the motor portion of the 

 par vagum, and the spinal accessory. 



In the movements of deglutition^ which are purely reflex^ the chief 

 eoxitor is the afferent portion of the glosso-pharyngeal, assisted by 

 the branches of the fifths distributed upon the fauces. The motor 

 nerves are the pharyngeal branches of the par vagum, assisted by 

 the facial, hypoglossal, motor portion of the fifth, and, perhaps, also, 

 the motor portions of some of the cervical nerves. The medulla ob- 

 longata is also concerned, in its reflex action, in governing the aper- 

 ture of the glottis, which it does through the agency of the superior 

 laryngeal branch of the par vagum, the afferent nerve, and the infe- 

 rior or recurrent laryngeal, the efferent or motor nerve. 



The medulla oblongata is connected, in its upward prolongations, 



