"In another instance, that of a female cat with kittens, something happened to create an anxious mood while the cat was attached to the holder. Until that moment the cat had been contented, and the work of digestion was proceeding normally. But now the movements of the stomach entirely ceased, and the gastric wall became relaxed. Only after the cat had been petted and began to purr did the stomach movements start again.
"I have observed the same thing in dogs and guinea pigs. A very slight emotional disturbance is enough to affect their digestion unfavourably."
Affecting specifically the brain, heart, arteries, stomach, intestines, liver, and glands of internal secretion, worry also has a general adverse effect on the nervous system.
This adverse effect is unmistakably expressed by the haggard, drawn, gaunt aspect of the man who habitually worries, and by his persistent sensations of fatigue. What has happened is that his nerve cells are being deprived of the nutrition they need in order to energise him properly. When, on the contrary, the worrier succeeds in changing his mental state—when he contrives to look at things confidently and contentedly—then, in the words of Professor George Van Ness Dearborn, there is a resultant and most beneficial increase in "the operative enthusiasm of the nervous system and of its affectors, the muscles and the glands."
The moral to parents is obvious. Keep children as joyous and happy as possible. By instruction and example, start them early in the path of emotional control. Protect them from needless causes of fear, worry, and anger. And make special efforts to prevent the development or continuance of that curious and most injurious mental attitude—the attitude of sulkiness—grounded in anger and frequently grounded also in sentiments of worry, envy, hatred, and even despair.