210 DIGESTION-MASTICATION, INSALIVATION, DEGLUTITION. 



The entire process of deglutition, therefore, occupies about six seconds. 



The muscular movements which take place during all the periods of deg- 

 lutition are peculiar. The first act is generally automatic, but it is under 

 the control of the will. The second act is involuntary when once begun, 

 but it may be excited by the voluntary passage of solids or liquids beyond 

 the velum pendulum palati. It is impossible to perform the second act 

 of deglutition unless there be some article, either solid or liquid, in the 

 pharynx. It is easy to make three or four successful efforts consecutively, in 

 which there is elevation of the larynx, with all the other characteristic move- 

 ments ; but a little attention will show that with each act a small quantity of 

 saliva is swallowed. When the efforts have been frequently repeated, the 

 movements become impossible, until time enough has elapsed between them 

 for the saliva to collect. 



All the movements of deglutition, except those of the first period, must 

 be regarded as reflex, depending upon an impression made upon the afferent 

 nerves distributed to the mucous membrane of the pharynx and oesophagus. 



The position of the body has little to do with the facility with which deg- 

 lutition is effected. Liquids or solids may be swallowed indifferently in all 

 postures. Berard saw a juggler pass an entire bottle of wine from the mouth 

 to the stomach, while standing on his head. The same feat was accom- 

 plished with apparent ease, by a juggler who drank three glasses of beer 

 while standing on his hands in the inverted posture (Flint). 



Deglutition of Air. In his essay on the mechanism of vomiting, Ma- 

 gendie stated that as soon as nausea occurred the stomach began to fill 

 with air, so that before vomiting occurred, the organ became tripled in size. 

 Magendie showed, fathermore, that the air entered the stomach by the oesoph- 

 agus, for the distention occurred when the pylorus was ligated. In a sub- 

 sequent memoir, the question of the deglutition of air, aside from the small 

 quantity which is incorporated with the food during mastication and insali- 

 vation, was farther investigated. It was found that some persons had the 

 faculty of swallowing air, and by practice, Magendie himself was able to ac- 

 quire it, although it occasioned such distress that it was discontinued. Out 

 of a hundred students of medicine, eight or ten were found able to swallow 

 air. 



It is not very uncommon to find persons who have gradually acquired the 

 habit of swallowing air, in order to relieve uncomfortable sensations in the 

 stomach ; and when confirmed, it occasions persistent disorder in digestion. 

 Quite a number of cases of this kind were reported by Magendie, and in sev- 

 eral it was carried to such an extent as to produce great distention of the 

 abdomen. A curious case of habitual air-swallowing was observed by the late 

 Dr. Austin Flint and is reported in his work on the Practice of Medicine. 



