THE MM ll \\ .|.,i - i i } }7 



sphincter, ordinarily contracted, relaxes for a momei hat th< 



passes into the stomach. In many animals, including man and tl 

 the peristaltic wave travels much more rapidly in the upper part of the 

 esophagus than lower down because of differences in the nature of the 

 muscular coat, this being of the striated variety above, and of th< 

 striated below. The purpose of more rapid movement in the upp< 

 is no doubl thai the bolus may be hurried past the rej . by 



distending the esophagus, it mighl interfere with the function of 

 boring structures, such as the heart. In other animi the dog, th< 



muscular fiber is striated all along the esophagus, and the boh 

 correspondingly travels at a uniform, quick rate all the way. [1 I 

 only about four seconds for the bolus to reach tl Lach in the dog. 



The peristaltic wave of the upper part of the esophagus in the cat a 

 presumably in man. unlike thai of the intestines see ■•■■- 

 mittcd by the esophageal branches of the vagus I • 



severed, but the muscular coats left intact, the esophagus becomes dih 

 above -the level of the section and contracted below, and no peristaltic 

 wave can pass along it; on the other hand, the muscular 



ered (by crushing, etc.) but t he peristaltic wave will conth 

 travel, provided no damage lias Pen done to the nerv< 



Tn the lower part of the esophagus, however, the wave of peristals 

 like that of the intestines, travels independently of extrinsic - 

 This has been observed in animals in which all of the extrinsic 

 have been cu1 some time previously. This differei en the up] 



and the lower portions is ated with the difference in the na1 



the muscular fibers above noted i Meltzer)." 



The propagation of ihe wave by the nerves in the upper part of 



esophagus indicates thai the se id stage and the first part of the third 



stage of deglutition must be r< sed, as it were, in the medullary 

 centers from which arise the nerve li : the pharynx and the np 



levels of the esophagus. It is thoughl that the dischai "om t ; 



local centers are controlled by a higher swallowing tuated in 



medulla just above that of respiration, the afferent stimuli ■ Inch 



pr ied from the pharynx by the fifth, superior lar; 



nerves. The exad location of thi ory areas wl timulation is 



most effective in initiating the swallowing reflex \ 



in different animals. in man it is probably at tl 



pharynx; in the dog it is on the posterior wall. A t body 



directly in the upper portion of the esophagus •• 



to remain stationary until the individual made llowing 



The afferent fibers in th< -■••'d ii' ful 



inhibitory influence on the deglutition • 



