All parents, indeed, ought to familiarise themselves with the physiology of anger and worry. Once really appreciative of the possible bodily effects of these emotional states, they would, on the one hand, be more careful to train their children early in emotional control, and, on the other, would be more chary about subjecting them to conditions involving emotional stress. Anger--and, equally, worry--is liable, for one thing, to derange profoundly the workings of the digestive organs. How profoundly it may derange them has recently been demonstrated conclusively by some remarkable scientific observations on animals and human beings. A prime requisite to good digestion is a free flow of saliva and gastric juice when food is chewed. There must literally be a preparatory automatic "watering" of the mouth and stomach. Ordinarily, this begins as soon as food is taken into the mouth--if one is hungry, it begins at the mere sight of food. But it has been proved that, no matter how appetising the food, the digestive flow stops almost altogether under the influence of anger. This was first demonstrated by a Russian physiologist, Pawlow, experimenting with dogs so conditioned that he could see into their throats and stomachs. When a dog was irritated--as by showing it a cat which it was prevented from attacking--the flow of saliva and gastric juice instantly stopped, and did not begin again for some time after the dog had been calmed. Even a slight degree of irritability in the animal was sufficient to stop gastric secretion. The same result has been repeatedly recorded by other scientists experimenting with cats, rabbits, guinea pigs, children, and full-grown men and women. One observer, a medical man named Hornborg, had as a patient a small boy in whom disease had caused an external opening large enough to allow a view of the workings of the stomach. Doctor Hornborg found that if he gave this boy food, after first angering him, his eating of the food was not accompanied by a flow of the gastric juice, which ordinarily flowed promptly and freely. And, besides stopping the secretory processes of the stomach, anger stops its muscular movements as well, and also the movements of almost all the alimentary tract. Hence, food eaten during or soon after an outburst of anger or petulance is not properly taken up by the alimentary canal for final digestion, absorption, and elimination. Which means, it need scarcely be pointed out, that every part of the body suffers in some degree through diminished nutrition. And certain specific discomforts are likely to be experienced--sour stomach, gastric pains, headache, and so forth.