in DIGESTION IN THE MOUTH AND STOMACH 167 



d'un certain temps, quand il sera arrive de nouvelle salive dans 

 la bouche ; enfin le cinquieme et le sixieme seront impossible, 

 parcequ'il n'y aura point de salive a avaler." 



Since deglutition normally takes place when the bolus or fluid 

 reaches the isthmus of the fauces, it is evident that the starting- 

 point of the reflex* is represented by the contact of the food with 

 the sensory nerve-endings distributed to this region. Wassilieff 

 (Bern, 1888), however, did not succeed in the human throat in 

 finding any point on the tongue, palate, or posterior and lateral 

 walls of the pharynx, at which mechanical, chemical, or electrical 

 stimuli incite the act of swallowing, as the stimulation of the 

 nasal mucosa incites sneezing, and contact with the glottis 

 coughing; we must assume that preparatory movements in the 

 isthmus of the fauces are required in order to excite swallowing in 

 man, these being absent during experimental excitation when the 

 throat is kept quiet. In the rabbit, on the contrary, deglutition 

 is infallibly excited on touching the central part of the anterior 

 surface of the soft palate, which is some 2-5 mm. broad, and 2 cm. 

 long, extending from the hard palate halfway along the tonsils. 

 The least contact in this region produces a complete act of 

 swallowing. Wassilieff succeeded in evoking fifty in succession 

 without finding any fatigue of the reflex nervous mechanism. 



K. H. Kahn (1903), who did much careful work on the reflexes 

 of deglutition, found that they were excited in the rabbit by 

 stimulation of the soft palate (trigeminal), in the dog and cat by 

 stimulating the dorsal surface of the pharynx (glosso-pharyngeal), 

 in monkeys by stimulation of the upper part of the palatal arch 

 (trigeminal). 



Both in rabbits and in man, anaesthesia of the sensory region 

 with a concentrated solution of cocaine (10-20 per cent) makes 

 the swallowing reflex impossible for some time (about a quarter of 

 an hour). This is the best proof that deglutition is not dependent 

 on will, as the respiratory movements are under certain conditions. 



The sensory fibres to the soft palate, which are the starting- 

 point of the swallowing reflex in the rabbit, derive from the 

 trigeminal, the sensibility of the palate to reflexes of deglutition 

 being permanently abolished after intracranial division of this 

 nerve. 



In 1865 Bidder and Blumberg noted that stimulation of the 

 central end of the superior laryngeal nerve also provokes move- 

 ments of swallowing. This fact was confirmed by A. Waller and 

 J. L. PreVost in 1870 for both cats and rabbits. 



They further found to their surprise that section of both 

 superior laryngeals produced no marked disturbance of deglutition, 

 particularly in rabbits, which survived for months after this 

 operation. On Kronecker's new theory this is not surprising, 

 since division of the superior laryngeals leaves intact the essential 



