This is generally due to an accumulation of gas in the intestines which forms there because the proteids (curd) of the milk are not digested. They should be reduced by using in the early months a weaker formula--i.e., instead of Formula V of the First or Second Series, IV might be used, or, for a short time, even III. The proteids may be reduced in the middle period by using weaker formulas If we desire to reduce the proteids without reducing the fat, we may change from the Second to the First Series. Another means of relieving habitual colic is the use of partially peptonized milk (page 115); still another the dilution with barley-water instead of plain water. _What change should be made if curds appear in the stools regularly or frequently?_ This is usually associated with habitual colic, and has to be managed exactly like that condition, by the means just described. _How should the milk be modified for chronic constipation?_ The constipation of the first weeks of life has been already referred to (page 82); it usually disappears as the food is gradually strengthened in all its proportions. Habitual constipation at a later period is difficult to overcome by diet alone. It sometimes depends upon the fact that the proteids are too high, and sometimes that the fat is too low. Hence it is more frequent when infants are fed upon plain milk variously diluted (page 90), then when 7-per-cent or 10-per-cent milk is used, and diluted to a greater degree. But it is not desirable to use a top-milk containing more than ten per cent fat for this purpose, nor is it wise to carry the fat in the food above 4 per cent (i.e., 8 ounces of 10-per-cent milk, or 12 ounces of 7-per-cent milk, in a 20-ounce mixture) or other disturbances of digestion may be produced. In some cases the use, in place of milk sugar, of ordinary brown sugar, in half the quantity, is of assistance; or of some of the malted foods (Mellin's food, malted milk, cereal milk) also in the place of milk sugar. The substitution of the milk of magnesia for the lime-water as recommended on page 60 will often be found useful. To infants over nine months old, orange juice may be given. _What special modifications are required during very hot weather?_ During the warm season it is well to make the proportion of fat less than during cold weather. During short periods of excessive heat it should be much less. The fat is reduced by using 7-per-cent milk in place of 10-per-cent (i.e., the Second instead of the First Series of formulas, page 71), or plain milk in place of the 7-per-cent milk in the Second and Third Series (page 90). At such times also the usual food should be diluted, and water should be given freely between the feedings. _What changes should be made in the food of a child who, with all the signs of good digestion, gains very little or not at all in weight?_