in DIGESTION IN THE MOUTH AND STOMACH 159 



mechanism of this act is one of the most difficult problems : 

 " difficillima -particula physiologiae," as Haller termed it. 

 Magendie (1808-13) was undoubtedly the one among modern 

 physiologists who occupied himself most with this phenomenon, 

 and his description, by its simplicity and clearness, leaves nothing 

 to be desired. He was the first to distinguish three stages in 

 deglutition : the first directed by the will, during which the bolus 

 passes from the mouth to the isthmus of the fauces ; the second 

 involuntary, of a reflex character, very rapid and almost con- 

 vulsive, in which the bolus passes the pharynx and reaches the 

 upper part of the oesophagus; the third involuntary, very slow, 

 carrying the bolus into the stomach. The mechanism by which 

 these three acts are performed is essentially the same ; it consists 

 in a peristaltic movement by which the bolus is driven onwards 

 and forwards in the first period by pressure of the tongue 

 against the palate, owing to contraction of the longitudinal lingual 

 and the mylohyoid muscles ; in the second by the contraction of 

 the constrictors of the pharynx, which surround and constrict the 

 bolus, carrying it forward, while the larynx and hyoid bone are 

 elevated, and the passage of the bolus through the aperture of the 

 glottis is accelerated ; in the third by the progressive contraction 

 of the circular fibres of the oesophagus, dilated by the pressure at 

 which the bolus is driven forward by the contraction of the 

 pharynx. 



Many details in Magendie's description are the fruit, not 

 merely of anatomical, but also of direct physiological, observation. 

 This explains how his theory came to be generally accepted, 

 subsequent physiologists only introducing slight modifications and 

 additions, with the object of completing and perfecting it in 

 various ways. 



In 1880, however, after the work of Kronecker and his pupils 

 and co-workers, doubt was for the first time cast on this doctrine in 

 regard to its central concept, viz. that the passage of the bolus from 

 the mouth to the stomach was effected by a comparatively slow 

 peristaltic contraction, by which it was driven from section to 

 section till it reached the stomach. In a paper with Talk, Kronecker 

 notes that when iced water is drunk, there is a feeling of cold in the 

 stomach directly after the first gulp, i.e. before peristalsis of the 

 pharynx and oesophagus can occur. Forensic medicine, again, has 

 described cases of poisoning by swallowing of corrosive fluids, which 

 showed on examination that the oesophageal lesions were confined 

 to certain isolated points, the greater part of the mucous membrane 

 being uninjured which would not be the case if the liquid 

 swallowed were propelled down the tube by peristalsis. Patho- 

 logical observation further shows that while paralysis of the 

 oesophagus makes deglutition difficult it does not inhibit it. 

 Kronecker concluded from these facts that the fluid or semi- 



