MOVEMENTS OF THE ALIMENTARY CANAL. 717 



contraction from one portion of the tube to another. This fact was 

 demonstrated by the experiments of Mosso,* who found that after 

 removal of an entire segment from the esophagus the peristaltic 

 wave passed in due time to the portion of the esophagus left on the 

 stomach side, in spite of the anatomical break. The same experi- 

 ment was performed successfully on rabbits by Kronecker and 

 Meltzer. Observation of the stomach end of the esophagus in this 

 animal showed that it went into contraction two seconds after the 

 beginning of a swallowing act whether the esophagus was intact or 

 ^ligated or completely divided by a transverse incision. A still 

 more striking proof of the same fact is the interesting case cited 

 by v. Mikulicz of a man in whom a portion of the esophagus 

 had been resected on account of a carcinoma. The lower end 

 of the esophagus was given a fistulous opening in the neck and 

 and it was found that food introduced into this opening was 

 not moved toward the stomach until the patient made a swallow- 

 ing movement, f The afferent nerves concerned in this reflex 

 are the sensory fibers to the mucous membrane of the pharynx 

 and esophagus, including branches of the glossopharyngeal, 

 trigeminal, vagus, and superior laryngeal division of the vagus. 

 Artificial stimulation of this last nerve in the lower animals 

 is known to produce swallowing movements. Several observers 

 have attempted to determine the precise area or areas in the 

 pharyngeal membrane from which the sensory impulses lib- 

 erating the reflex normally start. According to Kahn,t the 

 most effective areas from whose stimulation the reflex may be 

 produced vary in location in different animals. In the rabbit the 

 reflex is originated most easily by stimulation at the entrance to 

 the pharynx the soft palate along the line extending from the 

 posterior edge of the hard palate to the tonsils (superior maxil- 

 lary branch of trigeminal); in the dog irritation of the posterior 

 pharyngeal wall is most effective (glossopharyngeal nerve); in 

 monkeys the area is approximately as in rabbits, that is, in the 

 region of the tonsils. The motor fibers concerned in the reflex 

 comprise the hypoglossal, the trigeminal, the glossopharyngeal, 

 the vagus, and the spinal accessory. For an act of such complexity 

 and such perfect co-ordination it has been assumed that there is a 

 special nerve center, the swallowing or deglutition center, which has 

 been located in the medulla at the level of the origin of the vagi. 

 There is little positive knowledge, however, concerning the existence 

 of this center as a definite group of intermediary nerve cells, after 

 the type of the vasoconstrictor or respiratory center, which send 

 their axons to the motor nuclei of the several efferent nerves con- 



iv.i,uit;Huiiuut uuvexBuuuuiiKpUj JLO/U, volume AJ.. 



t Quoted from Cohnheim in Nagel's "Handbuch d. Physiologic." 

 j Kahn, "Archiv f. Physiologic," 1903, suppl. volume, 386. 



