in DIGESTION IN THE MOUTH AND STOMACH 169 



of the recurrens in the rabbit produced the same effect as that 

 of the superior laryngeal, i.e. a swallowing movement confined 

 to the upper tract which is innervated by the trigeminal, the 

 oesophagus being paralysed owing to the occlusion of the centri- 

 fugal paths contained in the two nerves resected. In morphinised 

 rabbits, reflex deglutition from the two laryngeals occurs less 

 readily than in the normal ; sometimes, however, when the 

 superior laryngeal is out of court, deglutition can be excited by 

 the interior laryngeal. After bilateral section of the two inferior 

 laryngeals, rabbits die in a few days from pneumonia owing to 

 the blocking of the oesophagus from the paralysis of its muscles. 



Fie. 57. Diagram of the four branches of the recurrens which supply different parts of the 

 oesophagus in rabbit. (Liischer.) c, va^us ; /, recurrens; 1, -i, 3, 4, its brandies ; 

 oesophagus; tr, trachea; It, border-line of thorax. 



The nerve centres which preside over and co-ordinate the 

 movements of swallowing lie in the upper part of the medulla 

 oblongata, for destruction of the brain above the respiratory 

 centres (more exactly above, and external to, the ali cineraee of 

 the rhomboidal sinus) does not abolish the movements of deglu- 

 tition (Wassilieff, Marckwald). We know, on the other hand, 

 from pathology that the so-called Imlbar paralysis produces 

 disturbance or inhibition of the act of deglutition. Nothing, 

 however, is known as to the localisation of these centres, on which 

 depends the co-ordination of the successive movements in the 

 various tracts (buccal, pharyngeal, oesophageal) of the alimentary 

 canal. 



The centrifugal paths (as may easily be inferred from the 

 above experiments) lie in the motor portions of the trigeminal 

 and hypoglossal nerves for the mylohyoid, hypoglossal, and lingual 



