SECRETION DIGESTION ABSORPTION. 



so, how does the time occupied in the passage of the wave com- 

 pare with the time before the gullet was divided ? 



If the peristaltic wave ceases to pass below the cut, what con- 

 clusion might you draw concerning the method of conduction of 

 the contraction wave ? If the wave continues to pass after the sev- 

 erance of muscular continuity, what conclusion might you draw ? 



9. Secure the vagus of one side with two ligatures and cut be- 

 tween. Again induce a swallow as before. Does the contraction 

 wave still pass over the oesophagus ? Explain. 



10. Now cut the other vagus also. Both vagus nerves are now 

 cut. Induce a swallow. Does the peristaltic wave continue to 

 pass over the oesophagus ? 



From the above observations what conclusions can you draw con- 

 cerning the mechanism of cesophageal peristalsis and the function 

 of the vagi in this connection ? 



11. The Vagus as a Motor Nerve to the Stomach. Enlarge 

 the abdominal incision so as to expose the whole of the stomach 

 including the beginning of the duodenum. Place the peripheral 

 ends of both vagi upon electrodes from an inductorium arranged 

 for medium strong tetanizing currents. Stimulate both vagi contin- 

 uously and note the strong contraction rings which pass over the 

 stomach from the fundus toward the pylorus. Note the opening of 

 the pyloric sphincter and the expulsion of a small quantity of stom- 

 ach content into the duodenum. Note the movements of the duo- 

 denum during and after the entrance of food from the stomach. 

 Keep the stomach covered with a pad of absorbent cotton moist- 

 ened with warm physiological saline, between observations. 



Over what part of the stomach wall are the contraction rings 

 most distinct and strongest? Where do they begin and in what 

 directions do they pass ? 



12. Stimulate both inferior laryngeal nerves. Note the effect 

 upon the upper segment of the oesophagus. What is the nature of 

 the musculature of the first part of the oesophagus ? 



13. Free the small piece of trachea connected with the cricoid 

 cartilage from blood and note the position of the vocal bands. 



9 [ I2 9l 



