218 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY 



testine about 20 cm. in length through this opening. The jejunum is 

 usually empty. If not, gently squeeze its contents along into the 

 lower bowel. Tie a ligature tightly about the middle of the exposed 

 segment, and a second and third about 8 cm. distally and centrally to 

 this one. In this way two segments of intestine have been isolated. 

 Into one of these inject 5 c.c. of a saturated solution of magnesium sul- 

 phate, and into the other 30 c.c. of a 0.7 per cent, solution of sodium 

 chlorid. Note that the former segment feels perfectly empty, whereas 

 the latter is highly distended. Replace the entire loop in the abdominal 

 cavity, marking its upper end with a colored piece of cord. Close the 

 opening in the abdominal wall with a clamp. Cover the animal with 

 a warm cloth and allow it to rest under anesthesia for thirty minutes. 

 At the end of this period expose the aforesaid segments and determine 

 their degree of distention. It will now be found that the loop contain- 

 ing the Mg SO4 is highly distended, whereas the loop with the NaCl is 

 practically empty. Obviously, the Mg SCX, possessing a greater osmotic 

 pressure than the body fluids, has abstracted water from the latter. 

 Contrariwise, the 0.7 per cent, solution of NaCl has been removed from 

 the loop. Using these facts as a basis, explain the action of the saline 

 cathartics. 



3. Chemical Stimulation of the Secretion of Intestinal Juice. 

 Insert a cannula in the external jugular vein, and empty a loop of 

 duodenum about 30 cm. in length. Inject intravenously from 1 to 

 3 c.c. of M/8 solution of barium chlorid or sodium citrate. Observe 

 the peristalsis which results almost immediately and measure the 

 quantity of intestinal juice obtainable from this segment. Kill the 

 animal by an excessive amount of ether. 



4. Gastric Fistula. Procure curved needle;-,, a needle-holder, and 

 clamps. Bring the wall of the pylorus in the wound and anchor it by 

 means of a continuous suture. Decrease the length of the wound by 

 sutures. Incise the gastric wall and suture it to the edges of the wound. 

 Insert a gastric cannula and secure it by additional sutures. 



5. Peristalsis. Anesthetize a rabbit and maintain the anesthesia 

 during the following experiments and until the animal has been killed 

 by an overdose of ether. Perform tracheotomy. Open the abdominal 

 cavity by a median incision through the linea alba. Observe the 

 peristalsis. The intestine of the rabbit invariably shows most intense 

 peristaltic movements when exposed to the cooler air or stimulated 

 mechanically. Note the pendular movements and also the regular 

 peristalsis. 



Compare the length and general appearance of the intestines of the 

 rabbit with those of the intestines of the cat and dog, noting especially 

 the predominance of the large intestine in the former animal. Discuss 

 the functional significance of this difference. 



6. The Influence of Salts on Peristalsis. Apply a few drops of 

 M/320 solution of barium chlorid or sodium citrate to the peritoneal 

 surface of a loop of intestine. Observe the marked peristalsis which 



