There are people who are up to weight or {154} slightly above it who develop tuberculosis, but they do not represent one in five of the patients who suffer from the affection. In probably three fourths of all the cases of tuberculosis the predisposing factor which allowed the tubercle bacillus to grow in the tissues was the loss of weight or the being underweight. There is a good biological reason for this, for there are certain elements in the make-up of the tubercle bacillus which favor its growth at a time when fat is being lost from the tissues rather than deposited, for at that time more fat for the growth of the tubercle bacillus is available in the lungs than at other times. Often among the poor the loss in weight is due to lack of food because of poverty, or failure to eat because of alcoholism, but not infrequently among all classes it is just a question of certain bad habits of eating that might readily have been corrected by the will. It is surprising how many people who complain of various nervous symptoms--meaning by that term symptoms for which no definite physical basis can be found, or for which only that extremely indefinite basis of a vague reflex, real or supposed, from the abdominal organs--are underweight and will be found to be eating much less than the average of {155} humanity. These nervous symptoms include above all discomforts of various kinds in the abdominal region; sense of gone-ness; at times a feeling of fullness because of the presence of gas; grumblings, acid eructations, bitter taste in the mouth, and above all, constipation. As is said in the chapter on "The Will and the Intestinal Functions," the most potent and frequent cause of constipation is insufficient eating, either in quantity or in variety. It is especially in the digestive tract of those who do not eat as much as they should that gas accumulates. This gas is usually thought to be due to fermentation, but as fermentation is a very slow gas producer and nervous patients not infrequently belch up large quantities, it is evident that another source for it must be sought. Any one who has seen a number of hysterical patients with gaseous distention of the abdomen and attacks of belching in which immense quantities of gas are eructated, will be forced to the conclusion that in such nervous crises gas leaks out of the blood vessels of the walls of the digestive tract and that this is the principal source of the gas noted. What is true in the severe nervous attacks is also true in nervous symptoms of other kinds, and neurotic indigestion so called {156} is always accompanied by the presence of gas.