138 DIGESTION AND ABSORPTION 



fusible has been absorbed by the time the residual material enters 

 the large intestine. This material consists chiefly of indigestible 

 substances and some water. The water is gradually absorbed 

 during the progress of the chyme along the large intestine. This 

 results in the waste material becoming more and more pasty as it 

 approaches the rectum for elimination. 



Hygiene of digestion. The body is normally in a state of health 

 and not disease. It is abuse of some kind that induces digestive 

 disturbances commonly called indigestion. Hygienic habits of 

 living make for good digestion. Activity in the open air and sun- 

 light, good food, relaxation, and rest are of prime importance. 

 Proper nutritional habits should be established. Meals should 

 be taken at regular intervals. If the digestive organs are worked 

 periodically, more regular digestive habits are established. As a 

 rule, food should not be eaten between meals, for it disturbs the 

 physiological routine and, also, interferes with the appetite. 



Since the alimentary canal is composed largely of muscles, exer- 

 cise is invaluable in keeping these muscles in proper tone. By 

 tone we mean the constant and unconscious tendency of the 

 muscles to contract under normal conditions. However, strenuous 

 exercise immediately after a meal is bad, as it withdraws much of 

 the blood from the digestive organs where it is needed, and sends 

 it to the active skeletal muscles that are working. This may re- 

 sult in indigestion and possibly muscular cramps. Consequently, 

 neither maximum digestion nor proper muscular activity is ob- 

 tained. This is one reason why persons are subject to digestive 

 or muscular cramp if they swim too soon after eating a heavy 

 meal. For a similar reason, undue excitement or mental stress 

 should be avoided during or after meals. Since the stimulation 

 of digestive glands is partly psychic (mental), violent emotions in- 

 terfere with the proper flow of digestive juices and withdraw the 

 blood from the digestive organs and send it to the brain and 

 nervous system. Pavlov, a famous Russian physiologist, learned 



