33 



Repeat this test with white flour and graham flour. 

 Which of these contains the more oil ? 



The digestive fluids of the body act on the foods which 

 we eat very much as ether acts on cheese ; they dissolve 

 the fats and make them ready for bodily use. 



EXPERIMENT 22. AN ARTIFICIAL EMULSION 



(a) Put a teaspoonful of lard, olive oil, or butter into 

 a test tube and add sufficient water to make the tube half 

 full. Do the two liquids mix? Shake vigorously. Do 

 they mix now ? 



(b} To the contents of the tube add a teaspoonful of 

 white of egg and shake the tube thoroughly. What is 

 the result? Such a mixture is known as an emulsion. 

 Oil and water alone will not mix, but upon the addition 

 of the white of egg, the oil separates into tiny drops, each 

 of which has a thin layer of egg around it, and these drop- 

 lets scatter themselves through the water and form an emul- 

 sion. 



A similar process is constantly occurring within our own 

 bodies. The fats and oils present in the foods which 

 we eat are not soluble in water alone, but they are broken 

 up by the intestinal fluids, and in the form of small drop- 

 lets are absorbed into the body tissue. The fats required 

 by the body are best obtained in a natural way, that is, 

 from the oil in milk, cheese, nuts, fatty meats, etc. 



Fat sometimes causes trouble in the body. For example, 

 the fat which accompanies fried food is unwholesome 

 because it forms a thick coating over and around the food 

 and keeps out the digestive juices. The food is thus 

 passed on, more or less undigested, to the intestines, which 



CL. LAB. 3 



