HOW FOOD IS DIGESTED 69 
7. Stomach digestion.—In the stomach, saliva contin- 
ues the digestion of the starchy matter, and is assisted 
by the gastric juice which pours in from the stomach lin- 
ing. This secretion has three constituents—acid, rennin, 
and pepsin. Pepsin is a ferment whose work is to split 
up the protein compounds. Rennin, also a ferment, as- 
sists in the digestion of milk. There is much of this 
secretion in calves. Gastric _ 
juice converts the protein - 
substances into peptones, The 
mucus glands of the stomach 
secrete mucin,a substance that 
lines the walls of the stomach. 
8. From stomach to intes- 
eA wt y 
: ‘ = core 
tines.—The constant churning eee 
movement in the stomach SromacH or Cow 
Showing the f ; 
causes the food to travel from OME he our COmPaniments 
its entrance to the small intestine. Up to this time there 
has been no absorption into the body; nor is digestion yet 
complete. When the partly digested material or chyme 
leaves the stomach it passes into the duodenum, one of 
the three parts of the small intestine, and is there sub- 
jected to further action by other digestive juices. Here 
the bile, the pancreatic and intestinal juices are admitted to 
complete the work. The bile, dark green or brownish in 
color, is secreted by the liver and acts in conjunction 
with the pancreatic juice. The pancreatic juice, 
alkaline and watery, is secreted by the pancreas, or 
“sweetbread.” 
. The bile acts as a bowel regulator when the liver is active and 
healthy. The pancreatic juice has a treble function—it changes 
starch into sugar, protein into peptones, and the oils into fatty acids. 
The intestinal juices perform a similar work. 
9. The two intestines are not only important for stor-. 
