85 



pi-esence of the food, contracts, and would in part send it back in a re- 

 trograde direction, by the nasal fossae, if the velum palati, elevated by 

 the action of the levatorcs palati, stretched transversely by the tensores 

 palati, was not applied to their posterior apertures, and towards the 

 openings of the Eustachian tubes. Sometimes this obstacle is overcome, 

 and the food returns, in part by the nostrils. This happens, when during 

 the act of deglutition, we attempt either to laugh or speak. At such 

 times, the air, expelled from the lungs with a certain degree of force, 

 elevates the epiglottis, and meeting the alimentary mass, pushes it back 

 towards the nostrils through which it is to pass. The isthmus faucium 

 is closed against the return of the food into the mouth, by the swelling 

 of the base of the tongue, raised by the action of the constrictor fauciura, 

 and of the constrictor pharyngis superior, which are small muscles con- 

 tained in the thickness of the pillars of the velum. 



The alimentary mass is directed towards the oesophagus, and is thrust 

 into that canal, by the peristaltic contractions of the pharynx, which may 

 be considered as the narrow 7 part of a funnel-like tube. The. solid food 

 passes behind the uperture of the larynx, which is accurately covered 

 over by the epiglottis. The liquids flow along the sides of that opening, 

 along two channels easily distinguished. They are always of a more 

 difficult deglutition than the solids ; the molecules of a fluid have an in- 

 cessant tendency to separate from one another, and to prevent this sepa- 

 ration, the organs are obliged to use greater exertion, and to embrace 

 with more precision the substance that is swallowed. Thus, it is to be 

 observed, in those cases in which deglutition is prevented by some or- 

 ganic affection of the oesophagus, that the patients, though they have the 

 power of swallowing solid food, find it difficult to swallow a few drops of 

 a liquid, and are tortured with thirst, though they have still the power 

 of satisfying their hunger*. 



The deglutition of air and of gaseous substances, is still more difficult, 

 than that of liquids, because these elastic fluids are much less coercible, 

 and it requires considerable practice, to transmit a mouthful of air- into 

 the stomach. M. Gosse, of Geneva, had acquired that power from re- 

 peated experience, and he made use of it to induce vomiting at pleasure, 

 and by the application of that faculty to the interests of science, he as- 

 certained the digestibility of the articles of food in most common use. 



-The food descends into the oesophagus, propelled by the contractions 

 of that musculo-membranous duct, situated along the vertebral column, 

 from the pharynx to the stomach. Mucus is secreted, in considerable 

 quantity, by the membrane which lines the inner part of the oesophagus, 

 it sheathes the substances which pass along it, and renders their passage 

 more free. The longitudinal folds of their inner membrane, allow the 

 oesophagus to dilate ; nevertheless, when it is stretched beyond measure, 

 severe pain is experienced, occasioned, no doubt, by thedistention of the 

 nervous plexuses, formed by the nerves of the eighth pair, which embrace 

 the oesophagus, as they course along its sides I purposely avoid speak- 



* Hydrophobia, presents us with the most distressing examples of this kind The 

 very sight or sound of fluids produce dreadful spasms of the muscles of deglutition ; 

 sometimes, even speaking of fluids has the same effect. Dr. Fothergill's case, pub- 

 lished in the London Medical Observations and Inquiries, may be particularly referred 

 to, as the patient throughout had not the slightest suspicion of the nature cf his disease, 

 and the dread could not have beeai imaginary. Godman. 



