172 THE HUMAN BODY, 



f. Half fill a test tube with the mixture c, add a toaspoonful of 

 the pepsin solution a, and then a few shreds of fibrin. Place in a 

 warm place for twenty-four hours. The fibrin will be more or less 

 completely dissolved at the end of that time. We thus find that 

 pepsin alone and dilute acid alone (at least in a moderate time) will 

 not dissolve proteids, but that acting together they quickly effect a 

 solution. 



4. The Action of Bile on Fatty Substances. a. Shake up some 

 olive oil with water in a test tube. The two liquids soon separate 

 when the shaking ceases. 



b. Obtain an ox gall from the butcher. Cut it open and collect 

 the bile. (The bile of herbivorous animals differs from human bile 

 in being green in color.) Shake up some oil with bile instead of 

 water. A creamy emulsion is formed from which the oil only slowly 

 floats up to the top. 



5. The Action of the Pancreatic Secretion on Fats. a. Obtain 

 a pig's pancreas; mince, and extract with about its own bulk of water 

 for two or three hours. Strain off the watery infusion. Add to it 

 half its bulk of oil in a test tube and shake thoroughly. The oil will 

 be very thoroughly emulsified ; and separate very slowly on standing. 



6. Action of Pancreatic Secretion on Starch. With some of the 

 watery extract of pancreas perform the experiments described above 

 under heading 2; substituting pancreatic extract for saliva. 



7. Action of Pancreatic Secretion on Proteids. a. Obtain a fresh 

 pig's pancreas. Lay aside in a cool place for twenty-four hours, 

 Mince, and extract for two days with twice its bulk of glycerine. 

 Strain off I he glycerine extract. 



b. Dilute the glycerine extract with ten times its bulk of water. 

 Place part of this mixture in a test tube together with some fibrin 

 shreds, and put aside in a warm place. After twenty-four hours 

 none of the fibrin will have been dissolved. 



c. To the diluted glycerine extract as above add a teaspoonful of 

 dilute acid (3 c). The fibrin will swell but not dissolve. 



d. To another portion of the diluted glycerine extract add just 

 sufficient bicarbonate of soda to make it distinctly alkaline, as tested 

 by litmus paper. Then put in some fibrin and set aside in a warm 

 place for a day. The fibrin will be more or less completely dissolved. 

 We thus find that the pancreas affords a substance which, in the 

 presence of weak alkalies, dissolves proteids. 



The fat-absorbing power of the lymphatics of the small intestine 

 is very readily demonstrable, without giving pain to an animal or any 

 unnecessary destruction of life. In most families superfluous kittens 

 or puppies have t6 be killed at the time of birth. Feed a kitten or 



