DIGESTION AND ABSORPTION 



339 



in No. 3 after shaking continues for a longer period than the same condition 

 in No. 4. Examine, under the compound microscope, a drop of the fluid 

 taken from tube No. 3. Notice the fluid appears to contain thousands 

 of tiny droplets of fat which float in the water surrounding them. Such 

 a mass of finely separated particles of oil and water is called an emulsion. 



Functions of Pancreatic Fluid. — From these experiments we see that 

 pancreatic fluid is alkaline in its reaction. It has the power, by means of 

 an enzyme called amolypsin, to change starches to sugars. A second enzyme, 

 called trypsin, changes proteids to peptones. Oils and fats, with the aid 

 of a third enzyme (lipase) are emulsified and in part changed to soap. 

 It is estimated that half an ounce of soap is formed daily in the small 

 intestine by this means. In such a form fats are enabled to pass through 





Appearance of milk under the microscope, showing the natural grouping of the fat globules. 

 In the circle a single group is highly magnified. Milk is one form of an emulsion. 

 (S. M„ Babcock, Wis. Bui. No. 61.) 



the walls of the intestine. This is, then, a form of digestion. The pancre- 

 atic fluid is thus seen to play a very important part in digestion, as it acts 

 upon all three nutrients, starches, proteids, and fats. 



Liver. — The liver is the largest gland in the body. In man, it hangs just 

 below the diaphragm, a little to the right side of the body. During life, its 

 color is deep red. It is divided into three lobes, between two of which is 

 found the gall bladder, a thin-walled sac which holds the bile, a secretion of 

 the liver. Bile is a strongly alkaline fluid of greenish color. It reaches the 

 intestine through a common opening with the pancreatic fluid. Almost one 

 quart of bile is passed daily into the digestive canal. 



Functions of Bile. — The action of bile on foods is not very well known. 

 It does have slight action in emulsifying fats. It is slightly antiseptic, 

 and is thus valuable in preventing fermentation within the intestine. Its 

 greatest importance, however, is the peculiar faculty it has of aiding the 

 passage of fats through the walls of the intestine. 



