MI DIGESTION 145 



The bile is in man a. golden -yellow, in ox and sheep a 

 yc-llowish-green, alkaline fluid, rather thick and slimy from the 

 presence of mucus formed by the walls of the gall-bladder, 

 and contains, besides the chlorides and phosphates of sodium 

 and other salts which are almost universally met with in the 

 body, certain peculiar salts which are found in it only. These 

 peculiar salts arc formed by the combination with sodium of 

 two peculiar organic acids. The salts so formed arc spoken 

 of as the bile-salts. There is also present a peculiar fatty- 

 looking, crystallisable substance called cholesterin. The yellow 

 or green colour is due to the presence of a colouring matter 

 or pigment, which is formed by the liver from the colouring 

 matter, haemoglobin, of red blood corpuscles. 



Digestion in the Intestine. When the chyme passes 

 through the pylorus, the pancreas secretes its juice, and as this 

 is gradually pouretl into the duodenum, a quantity of bile is 

 discharged from the gall-bladder or from the liver at the same 

 time, and the chyme is mixed with these two fluids. The chyme 

 from the stomach is acid, and the first effect of the alkaline 

 bile and alkaline pancreatic juice is to neutralise the chyme and 

 then to make -it alkaline. By this any further action of the 

 gastric juice carried along in the chyme is stopped, for pepsin 

 cannot act in an alkaline fluid. The pancreatic juice then acts 

 on the starch which has escaped the action of saliva, and turns 

 it into malt-sugar. No doubt a considerable amount of starch 

 escapes the salivary digestion as the stay of the food in the 

 mouth is short. The amylolytic ferment of the pancreatic 

 juice is very like the ptyalin of saliva, and like it acts in an 

 alkaline medium. Any proteids which have escaped the 

 action of the gastric juice are turned into peptone by the 

 pancreatic juice. The proteolytic ferment of the pancreatic 

 juice is like the pepsin of the gastric juice, but differs from it 

 in being able to act in an alkaline fluid only, while the latter 

 can act in an acid fluid only. The bile has no action on 

 carbohydrates or on proteids, but both the pancreatic juice 

 and the bile act on fats. 



Digestion of Fats. The carbohydrates and the proteids 

 .nc i hanged chemically in the process of digestion, and rendered 

 soluble. The fats, on the other hand, arc not changed 

 chemically and arc not rendered soluble. In the process of 



