114 LABORATORY EXERCISES 



c. Rennet. Into a bottle put about 50 cu. cm. of milk, and 

 set the bottle in a dish of water at 37 to 38 C. (about 100 F.). 

 Add some commercial rennet, or a " junket" tablet. Keep the 

 milk warm for about 10 minutes; then set it aside. What hap- 

 pens? Which part is curd? Whey? What does each contain? 



d. Pancreatic Juice. Dissolve a little commercial pan- 

 creatin, or pancreas extract, in warm (not hot) water; divide 

 the solution into two parts. Add half of the pancreatin solu- 

 tion to a tablespoonful of olive oil and the same volume of warm 

 water. Set the mixture in a warm place. Shake up the mix- 

 ture from time to time for 2 or 3 days. Note what happens. 



Make a smooth starch paste by mixing a teaspoonful of 

 starch with 3 or 4 teaspoonfuls of cold water. Set the paste 

 in a pan of warm water, and add to it the other half of the 

 pancreatin solution. Let it stand for at least a day, and note 

 what happens. If possible, test the product with Fehling's 

 solution? Has the starch been changed to sugar? 



EXERCISE 104 

 THE BLOOD VESSELS 



Apparatus and Materials. String, stethoscope (get it from a physi- 

 cian), heart of sheep or calf, with the connecting organs. 



a. Press with three fingers upon the artery in the wrist, 

 and count your pulse beats. How many are there each min- 

 ute? In the same way "take the pulse" of an old person, and 

 of a young child. Compare the number of beats. 



Take some vigorous exercise, or breathe very deeply a num- 

 ber of times; what is the effect upon your pulse? 



b. Find the large veins on the back of your hand. Press the 

 blood out of one of them by pushing down hard with a finger of 

 your other hand and at the same time moving the finger from 

 the wrist toward the knuckle. Notice that blood does not 



