LESSON XLIII 



DIGESTION 



DEGLUTITION 



1. Isolation of the Esophagus. Anesthetize a mammal and main- 

 tain the anesthesia throughout the following experiments: Perform 

 tracheotomy low down. Separate the trachea from the esophagus, and 

 excise the piece of trachea situated between the cricoid cartilage and 

 the metal cannula. Palpate the esophagus, noting its texture and 

 movability. 



Expose both vagi nerves and place them in loose ligatures. In 

 addition, expose their superior laryngeal branches and place them in 

 loose ligatures. 



Make a median incision through the linea alba. Follow the an- 

 terior wall of the stomach until the esophageal gastric junction has 

 been reached. Insert a straight cannula in the orifice of the esophagus, 

 and connect it with a manometer containing water. Cover the ab- 

 dominal wound with a cloth moistened with warm saline solution. 



2. Wave of Deglutition. Open the mouth of the animal and touch 

 the fauces with a moistened plug of cotton. Observe the swallowing 

 movements evoked thereby. Note that they begin in the mouth and 

 travel downward in the form of a peristaltic wave, involving the different 

 segments of this passage consecutively. 



Observe the displacement of the column of water, and determine 

 approximately the interval of time between the beginning of this act 

 and the moment when the wave has reached the level of the larynx, 

 and again when it has arrived at the cardiac end of the stomach. In 

 which segment is its progress slowest? 



Evoke these movements by stimulating the central end of the 

 superior laryngeal nerve. 



3. Division of Esophagus. Cut transversely across the cervical 

 portion of the esophagus. Stimulate the central end of the superior 

 laryngeal nerve, evoking peristalsis. Does the wave proceed as before, 

 or is it blocked at the line of the section? Explain. 



Raise the orifice of the lower segment slightly. Insert an elliptic 

 piece of smooth wood secured by means of a thread. Does the intro- 

 duction of this body lead to a wave of deglutition in this segment? 

 If not, excite a wave in the normal way, either by stimulating the 

 superior laryngeal nerve or by stimulating the mucous membrane of 

 the mouth. Is the wood now propelled onward? Explain. 



4. Influence of the Vagi Nerves. Divide the right vagus nerve. 

 Excite deglutition by stimulation of the superior laryngeal nerve. Study 

 the character of the wave. Divide the left vagus nerve and repeat this 



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