MOVEMENTS OF THE ALIMENTARY CANAL, ETC. 313 



food into the stomach occurs in man about six seconds after the beginning of 

 the act of swallowing. 



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

 mechanism of swallowing 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. By 

 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 oesophagus, the time elapsing between the beginning of the swal- 

 lowing movement and the arrival of the food at the cardiac orifice of the 

 stomach being not more than 0.1 second. The contraction of the constrictors 

 of the pharynx and the peristaltic wave along the oesophagus, according 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 frag- 

 ments along the deglutition passage, or possibly, in case 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 to actually push the bolus downward, 

 although at a much slower rate. From auscultation of the deglutition sound 

 which ensues when the food enters the stomach through the cardia, Kronecker 

 and Meltzer believe that usually the swallowed food after reaching the end of 

 the oesophagus is kept from entering the stomach by the tonic contraction of 

 the sphincter at that point, until the subsequent peristaltic wave of the oesoph- 

 agus, which reaches the same point in about six seconds after the beginning of 

 the act of swallowing, forces it through. There are, however, exceptions to 

 this rule. In some persons, apparently, the food is forced into the stomach by 

 the energy of the first contraction of the mylo-hyoid muscles. The difference 

 would seem to depend upon the condition of the sphincter at the cardiac 

 orifice. Moreover, these authors were able to determine by their method of 

 recording that 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 beginning of 

 swallowing and is comparatively short, lasting 2 seconds, corresponding to the 

 1 Du Eois-Reymond's Archw fur Physiologic, 1883, Suppl. Bd., S. 328. 



