MOVEMENTS OF THE ALIMENTARY CANAL, ETC. 375 



food into the stomach occurs in mail about six seconds alter the beginning of 

 the act of swallowing. 



Kronecker-Meltzer Theory of Deglutition. — The usual view of the 

 mechanism of -wallowing has been seriously modified by Kronecker and 

 Meltzer. 1 The experiments of these observers seem to be so conclusive that 

 we must believe that in the main their explanation of the process is correct. 

 According to their view the chief factor in forcing soft or liquid food through 

 the pharynx and oesophagus is the sharp and strong contraction of the mylo- 

 hyoid muscles. The bolus of food lies upon the dorsum of the tongue and 

 by the pressure of the tip of the tongue against the palate it is shut off from 

 the front part of the mouth-cavity. The mylo-hyoids now contract, and the 

 bolus of food is put under high pressure and is shot in the direction of least 

 resistance — namely, through the pharynx and oesophagus. This effect is aided 

 by the simultaneous contractions of the hyoglossi muscles, which tend to still 

 further increase the pressure upon the food by moving the tongue backward 

 and downward. This same movement of the tongue suffices also to depress 

 the epiglottis over the larynx, and thus protect the respiratory opening. Bv 

 means of small rubber bags connected with recording tambours, which were 

 placed in the pharynx and at different levels in the oesophagus, they were able 

 to demonstrate the rapid spirting of the food through the whole length of 

 pharynx and into the oesophagus, the time elapsing between the beginning of 

 the swallowing movement and the arrival of the food at the lower end of the 

 oesophagus being not more than 0.1 second. The contraction of the con- 

 strictors of the pharynx and the peristaltic wave along the oesophagus, ac- 

 cording to this view, normally follow after the food has been swallowed, and 

 may be regarded as a movement in reserve which is useful in removing 

 adherent fragments along the deglutition passage, or possibly, in cases of the 

 failure of the first swallowing act from any cause — as may result, for instance, 

 in swallowing food too dry or too solid — serves actually to push the bolus 

 downward, although at a much slower rate. From auscultation of the deglu- 

 tition sound which ensues when the food enters the stomach through the 

 cardia. Kronecker and Meltzer believe that usually the swallowed food alter 

 reaching the lower portion of the oesophagus does not enter the stomach 

 until the subsequent peristaltic wave of the (esophagus, which reaches the 

 same point in about six seconds after the beginning of the act of swallowing, 

 forces it through. According to Cannon and Moser, 2 the rapid projection of 

 food into the deeper part of the (esophagus occurs only with liquids. When 

 the food is solid or semisolid peristalsis is required to move the bolus through 

 the oesophagus. Kronecker and Meltzer were able to determine hv their 

 method of recording thai the human oesophagus contracts apparently in three 

 successive segments. The first of these comprises about six centimeters in 

 the neck region, and its contraction begins about 1 or 1.2 seconds after the 



1 Archiv f ii r I'litfslnlof/ir, 1883, Suppl. I'd., S. 328 ; also Journal of Experimental Medicine, 

 1897, vol. ii. p. 453. 



2 American Journal of Physiology, 1898, vol. i. p. 435. 



