. The human body and health : an elementary text-book of essential anatomy, applied physiology and practical hygiene for schools . nds completely lining the interior ofthe stomach manufacture from the blood the gastric glands are made to act either by the taste and odorof food or by the presence of food in the stomach. At thebeginning of the meal certain foods, such as cake, bread,and potatoes, cause a much less flow of juice than soupsand meat. On this account a small amount of soup at thebeginning of the meal is helpful to digestion. As a pleas-ing odor and taste tend to increase t
. The human body and health : an elementary text-book of essential anatomy, applied physiology and practical hygiene for schools . nds completely lining the interior ofthe stomach manufacture from the blood the gastric glands are made to act either by the taste and odorof food or by the presence of food in the stomach. At thebeginning of the meal certain foods, such as cake, bread,and potatoes, cause a much less flow of juice than soupsand meat. On this account a small amount of soup at thebeginning of the meal is helpful to digestion. As a pleas-ing odor and taste tend to increase the amount of stom-ach secretion, the kind of food easily digested by one per-son may cause dyspepsia in another. Grief or mentalexcitement tend to decrease the action of the gastricglands. Movements of the Stomach. — In order that the foodmay be moved forward and mixed with the gastric juice,the stomach must perform certain movements. It wasonce thought that these movements were of such a natureas to cause the contents of the organ to pass round andround from one end to the other. Lately it has been 94 HOW FOOD IS DIGESTED. shown by the use of the X rays on man and by experimentson rats that no such rotary motion of the food large end of the stomach has little or no motion, whilecontraction of the circular fibers begins about the middleand extends toward the pylorus, squeezing and mixingthe food with the juices. One wave of contraction afteranother begins at the middle and progresses toward the small intestine, tendhigto press the contents ofthe stomach into the in-testine. The materialis prevented from leav-ing the stomach bythe contraction of aring of muscle, the py-„ ..A rru . 1, , ^1, • 1 loric valve, which re- FiG. 60. — The stomach, with the circular muscle fibers removed from the right half laxes only when pushcdto show the other muscular fibers. ^ • „w- i t • i against by a Required for Digestion. — The length of time re-quired
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