18 LABORATORY GUIDE IN PHYSIOLOGY. 



incision through the xiphoid appendix and abdomi- 

 nal walls. Withdraw the pins which fix the anterior 

 extremities; separate the lateral halves of the ster- 

 num by lateral traction upon the legs. 



(3) With the forceps grasp a fold of the mucous 

 membrane which surrounds the puckered anterior 

 end of the oesophagus. While making gentle trac- 

 tion with the forceps, make, with the fine scissors, 

 a circular incision through the mucous membrane 

 surrounding the opening of the oesophagus. 



(4) Grasp the pyloric end of the stomach; sever the 

 duodenum; lift the stomach up vertically above the 

 sternum; make moderate traction. The delicate and 

 elastic submucosa about the end of the oesophagus 

 will yield to the traction and the whole oesophagus 

 will be readily separated from the surrounding tis- 

 sues and w"holly removed from the frog. 



(5) Open stomach and oesophagus by means of a 

 longitudinal incision through their walls; stretch 

 them upon a cork board, fixing with pins, and wash 

 off mucus with normal saline solution and camel's 

 hair brush. Remove the excess of liquid with the 

 help of filter paper. 



4. Observations. 



(1) Place a small piece of cork upon the anterior end 

 of the oesophagus. Does the cork move? li so, in 

 what direction and at what rate ? 



(2) Will the cork pass over the boundary line between 

 oesophagus and stomach, and will it move over the 

 surface of the stomach? 



(3) To determine the cause for the movement of the 

 cork, cut a minute portion of mucous membrane 

 from the crest of one of the folds, place it in a drop 

 of saline solution as directed under 2 {Preparation} 



