16 THE FUNCTIONS OF ANIMALS. 



high teftiperature, I and form an imperfect emulsion. The 

 stomach is now g't-adually emptied, partly by the escape of 

 the semi-digested food through the lower opening, and 

 partly by the absorption of dissolved parts into the blood. 

 The semi-digested food, as it passes out of the stomach into 

 the small intestine, is called chyme; when it reaches the 

 opening into the intestine of the bile duct, and of the duct 

 from the pancreas, a flow of bile and pancreatic juice takes 

 place. These being both alkaline tend to neutralise the 

 acidity of the chyme, and their other uses are as follows : — 

 The conversion of starch into sugar is recommenced by a 

 ferment in the pancreatic juice ; by another ferment the fats 

 are emulsified, that is, the drops become extremely small, 

 and so can be absorbed ; a third ferment splits the fats 

 into fatty acids and glycerine. The acids are converted into 

 soaps to a certain extent by the alkaline contents of the 

 intestine, this favours the process of emulsification in 

 which the bile also takes part. On proteids the action of 

 the pancreatic juice is similar to that of the gastric juice; the 

 ferment in this case is called trypsin. It acK in a neutral 

 fluid, whereas pepsin requires the presence of hydrochloric 

 acid. The pancreatic juice is there fore a very poVerful one, 

 repeatiiT g with some additions all t h e^digggtive- proc e sscy tif 

 the other gland s :-— 



(i) transforming starch into sugar j ^ 



(2) transforming proteids into soluble peptones; 



(3) emulsifying fat; 



(4) splitting fats into fatty acids and glycerine. 

 The powers of bile may be summarised as : — 



(i) in some animals, a slight power of converting starch 



into sugar ; 

 (2) by its alkalinity, preparing the way for the action ot 



trypsin ; 

 {3) a slight solvent action on fats, a slight emulsifying 



power, and the formation of soaps with fatty acids; 



(4) in affecting cell-membranes so that they allow the 



passage of small drops of fat and oil ; 



(5) various antiseptic qualities. 



In addition to the liver and pancreas, there are on the 

 walls of the small intestine a great number of small glands 



