Cases of fat indigestion may also be treated by means of buttermilk, which is very similar in composition to skimmed milk. It differs in the markedly acid reaction, due to the lactic acid fermentation, and in the casein formed in the stomach, which is casein lactate instead of calcium casein. Casein lactate is not acted on by rennin and consequently does not form dense curds in the stomach. Lactic acid is believed to check the growth of certain putrefactive and pathogenic bacteria in the gastro-intestinal tract, and to aid in the peptonization of the milk. These combined advantages have led to the successful employment of buttermilk in cases of chronic indigestion. Buttermilk may be obtained in many country places fresh from the churn, and this is probably the most efficient form in which it can be given. In towns it is sold by many of the large dairy companies, or it may be artificially prepared at home by the use of "lacto-bacilline." Lacto-bacilline is fluid milk which contains the bacillus acidi lactici. It is used in the following way to prepare "lactated milk" (Batten). Fresh milk is boiled, and then cooled down in a sterilized stoppered bottle to 96° F. One tube (about 3 drachms) of lacto-bacilline is added to 11 oz. of milk. The milk is kept in a water bath at a temperature of 96° F. for seven hours, during which time it becomes sour, and a slight clot is formed. It is next cooled on ice for twelve hours, at the end of which time it has become a creamy fluid and is ready for use. Batten found that children who could not take any other form of milk could retain and digest lactated milk. When fat indigestion is the source of trouble one can use either fresh buttermilk or the lactated form made from skimmed milk. In both cases the buttermilk is only a temporary measure, and fat in some form must be added to the diet later on. The addition also of large quantities of lactic acid is believed to affect injuriously the chemical metabolism of the system, if this method of feeding is unduly prolonged. Separated milk, i.e. milk with all the cream removed, may also be employed as a temporary measure in cases of fat indigestion.

One or other of the above measures will usually prove effective, but in exceptionally difficult cases of chronic indigestion one may employ condensed or dried milk. A good brand of sweetened condensed milk, with all the original cream present, should be obtained. It must be given well diluted, one tea-spoonful of the milk to 4 or 6 oz. of water to begin with, according to the age and state of the infant. The strength is to be gradually increased as toleration is established. Again one of the dried milks, such as plasmon, or somatose, or sanatogen may prove useful. The dilution, to begin with, should be one teaspoonful of the powder to 6 oz. of water. Why it is that milk in these forms should apparently be better tolerated than fresh preparations is difficult to explain, but it is probably due to some change in the proteins which are rendered more digestible. In the case of infants under six months starchy foods are not to be recommended for digestive troubles. After that age they may sometimes be found useful, possibly from their mechanical action in reducing the size of the curds. The flour of barley or oatmeal or wheat may be used. A tablespoonful of one of these is to be boiled in a pint of water for an hour. Of this half to one ounce may be mixed with an ordinary feed of milk and water. At this age also one may sometimes aid the digestion of the milk by adding a small quantity of one of the converted starch preparations, such as Mellin's food, care being taken that not more than a half to one teaspoonful be given as a meal.

These are some of the more common dietetic methods now employed for meeting the digestive difficulties of infancy. At the outset one must not only decide on the food, but proceed to give it a fair trial. The effect will not be seen all at once, and if the food is varied every few days there will probably be no improvement. At least a week or ten days are required to test the effect. At the same time it is often quite a good plan to combine two of the methods, giving for instance a diet of peptonized milk by day and of whey by night. Both of these preparations are for the same purpose, namely, to reduce the amount of protein digestion in the stomach, and one may be able to tell from the symptoms which is most effective and to act accordingly. A little variety in the diet may also aid the stomach and bowels in recovering their tone.

Perhaps more important than the food is the degree of dilution. The digestive powers are weakened and inactive, and only the weakest foods will be tolerated. Hence the most excellent foods may prove useless simply because they are too strong. At the same time the stomach must not be flooded by large quantities of fluid food. Small amounts frequently repeated are better than larger quantities less often. It is best to begin with 1-2 oz. every hour, or 2-3 oz. every two hours.

One may sometimes be at a loss to know whether the food is really agreeing with the infant. Favourable signs are a cessation of the whining and restlessness, the recurrence of smiling, and longer and quieter periods of sleep. The subsidence of the active gastro-intestinal symptoms, flatulence, colic, etc., and an improvement in the quality of the stools are favourable indications. A gain in weight is not to be looked for at once, as the diet in the early stage is one to rest the alimentary tract, not to fatten the child. It is not until all active signs have subsided and a more nourishing food has been adopted that the nutrition of the infant will improve. In the early stages also the amount of fat must be reduced to a minimum, owing to its indigestibility. In the convalescent stage, on the other hand, cream and cod-liver oil are of the greatest benefit in building up the patient.

The duration of the special feeding will depend on the severity and length of the illness. It must always be kept in mind that however useful as temporary measures, these methods of feeding should not be prolonged further than is necessary, because dangers lurk in the way. As soon as possible the infant should return to a diet of fresh cows' milk and other materials suitable to its age, as already described. The return to normal diet must be made gradually, by introducing one or two feeds of fresh milk in the course of the day.