LESSON XLVI 



DIGESTION (Concluded) 



LACTEALS AND THORACIC DUCT. PERISTALSIS. SECRETION OF BILE 



1. Lacteals. Anesthetize a cat which has been fed with fatty food 

 several hours beforehand, and maintain the anesthesia throughout the 

 following experiments: Perform tracheotomy. Open the abdomen by 

 a longitudinal cut in the median line, and thus expose the viscera. 

 Throughout the subsequent experiments keep the viscera warm by 

 applying cloths moistened with warm physiologic salt solution. Ex- 

 amine the walls of the intestine and the mesentery. Identify the lac- 

 teals filled with chyle, and note their beaded appearance. These con- 

 strictions indicate the positions of the lymphatic valves. Trace the 

 lacteals to the receptaculum chyli, the enlarged abdominal end of the 

 thoracic duct, which lies opposite the kidneys. 



2. Peristalsis. In the cat, spontaneous peristaltic movements of 

 the small intestine are seldom in evidence. Give reasons for this 

 motor quiescence. Stimulate the intestine mechanically and elec- 

 trically and watch the resulting contractions. 



Is the stomach contracting? Stimulate its surface at the fundus 

 and at the pylorus. Compare the results. 



Expose the right vagus nerve; cut it, and stimulate its distal stump. 

 Observe the movements of the stomach and intestine. What is their 

 character? 



3. Chyle. Slit open a distal lacteal. With a pipet transfer a few 

 drops of chyle to a watch-glass and observe the coagulation. Place a 

 drop on a glass slide and examine it microscopically, identifying white 

 corpuscles and fat globules. Close the opening in the lacteal by means 

 of an artery clamp. 



Expose the region of the hepatic artery and trace the numerous 

 lymphatics to the hilum of the liver. What is their appearance? What 

 is the character of their contents? 



4. Secretion of Bile. Ligate the common bile-duct just above its 

 entrance into the duodenum, and insert a cannula in its hepatic end. 

 Empty the gall-bladder by gently squeezing it between your fingers and 

 occlude the cystic duct by means of an artery clamp. Connect the 

 cannula with a graduated cylinder. Read off the quantity of bile so 

 far collected. Note the effect upon its level of the respiratory move- 

 ments. Ascertain by reading the amount of bile that is secreted in a 

 given period of time. After fifteen minutes place the graduated cyl- 

 inder in a vertical position, and determine the pressure under which the 

 bile is being secreted. What is the relationship between the secretory 



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