When the cows are employed in ploughing, etc., or in drawing carts, not only are the calves fed at long intervals, but the milk is not always of proper chemical composition even in the udder. As a result of work, fatigue, over-exertion and irregular feeding, the cow’s yield of milk for the time is less digestible than the normal supply, or may even prove irritant to the calf’s stomach. Milk indigestion is thus set up. When the cows are fed on factory waste, like beetroot-pulp or brewers’ grains, toxic or irritant products may even find their way into the milk, which then irritates the little creature’s abomasum and produces gastric indigestion. Just as in the production of congenital alcoholism in man, the young animal is then ingesting, unknown to those responsible for its well-being, chemical substances which produce various pathological changes. But milk indigestion is commonest of all in calves fed by hand. The food usually given is a mixture of milk from the previous night, and skim milk or even butter milk. It contains lactic ferments and various microbes, some capable of producing toxic principles. When swallowed and brought directly in contact with the mucous membrane these cause abomasal indigestion. =Symptoms.= Soon after feeding, the little animal appears dull and somnolent, and shows moderate abdominal pain, suggesting trifling colic. This stage is soon followed by nausea; the breathing and the heart’s action become rapid, vomiting efforts are made, and finally milk, in the form of firm or partially softened curds, depending on the time which has elapsed since the last feed was taken, are vomited. The quantity ejected varies. Pressure over the right side of the abdomen produces pain, and tympanites of the abomasum may sometimes be detected on percussion. The sensitiveness and gaseous inflation are confined to the middle and lower zone of the hypochondrium. Soon after vomiting the animal begins to improve. The patient seems brighter, relief is very marked, and in some cases proves permanent; but more frequently a certain degree of depression persists, the mouth emits a sourish odour, and for a time the appetite remains poor. This temporary irritation of the abomasum has a tendency to become permanent; or even to extend to the intestine, in which the conditions appear more favourable to the development of microorganisms than do those in the stomach. Indigestion then becomes complicated with diarrhœic enteritis. =The diagnosis= presents no difficulty. =The prognosis= is not serious, provided that the young animals are carefully attended to; but such complications as diarrhœic enteritis may become very grave if neglected. =The treatment.= To prevent recurrences: (1) The periods of feeding should be regulated; (2) The cows should not be worked, or should be worked as little as possible; (3) Mixed milk, or milk which has already undergone lactic or other fermentation, should be avoided.