86 



ELEMENTARY BIOLOGY 



The pancreatic juice thus contains all the kinds of ferments 

 necessary for digesting a whole meal. 



121. The liver. The juice produced by the liver is called 

 the bile, or gall. 



I. It does not contain any ferments that seem to be impor- 

 tant in digestion, but it does have an influence on the absorp- 

 tion of the fatty acids 

 and soaps by the cells 

 of the intestine. 



2. The bile seems 

 further to have some ef- 

 fect upon the activity of 

 the pancreatic ferments. 

 When the contents of 

 the stomach pass into the 

 intestine, the mixture is 

 acid ; the bile neutral- 

 izes the acid and makes 

 possible the activity of 

 the other ferments. 



3. The bile is made 

 up chiefly of materials 

 that are of no further 

 use to the body — ma- 

 terials that have been 

 converted in the liver 

 and are then thrown 

 into the intestine, fjom 



which they are removed from the body. The liver is thus 

 also an excretory organ. 



122. The intestinal juices. The juices secreted by the glands 

 of the intestine contain no ferments that are of great importance in 

 digestion, although they do contain a great deal of sodium carbonate, 

 which neutralizes the acids resulting from the digestion of fats by the 

 pancreatic juice, and probably also other acids resulting from other 



Fig. 31. The lining of the intestine, (x 150) 



The tiny projections from the lining of the small 

 intestine, the villi^ give the appearance of very fine 

 velvet. Absorption takes place through the outer 

 layer of cells. W^ithin each villus are fine blood ves- 

 sels and lymph spaces ; from these the absorbed food 

 is transferred to circulation system 



