A number of concentrated invalids' foods are upon the market. Some of them are extremely useful in increasing the amount of certain nutritive ingredients that are needed, and in helping to force alimentation when there is a disinclination to eat. They are important aids in the maintenance of strength - (1) When little food can be taken at a time; (2) when swallowing is painful or difficult; (3) when there is a disgust for food and only a small quantity will be taken; (4) when it is desirable to force upon patients a large amount of nourishment.

Food can be concentrated only to a moderate extent. Meat when desiccated affords a weight of protein equal to one-fifth its original weight. Sugar is the most concentrated form of carbohydrate. Olive oil is a type of the most concentrated oil or fat.

When food is taken in concentrated form, it taxes the digestive organs to secrete juices to digest it, and its bulk is often insufficient to stimulate the stomach to muscular efforts adequate to expelling it promptly. So, even when food has to be administered in its most concentrated form, sufficient water should always be given to dilute it in the stomach, and to give a certain bulk or volume to the contents of the viscus.

Concentrated foods are not well adapted for exclusive use, but they are most useful when employed to increase the percentage of certain of the proximate principles of food.

Concentrated proteins are made from milk, eggs, meat, and vegetables. They are sometimes partly predigested. Meat powder is desiccated lean meat finely ground. This can be made at home, or such a preparation as Mosquera's may be used. There are many varieties of predigested meat powder. They contain albumoses, or mixtures of albumoses and peptone. Meat powder and peptones are not agreeable to the taste of all patients. To disguise this taste, however, they may be given with other foods or beverages - as, for instance, in gruels or broths, or in coffee or coacoa. Somatose, which is a mixture of albumoses, has little or no taste and is therefore easy to administer. A teaspoontul is equal to a half ounce of meat in nutritive value. Neutrose, eucasein, and plasmon are made from casein. They also are tasteless, colorless, and readily soluble. Aleuronat and legumin are foods composed chiefly of vegetable proteins. Tropon is composed of egg-albumen and protein of vegetable origin.

Many of the peptone preparations upon the market do not contain a protein in highly concentrated form; for instance, Armour's wine of peptone and Fairchild's panopepton contain only 3 per cent. But they both contain considerable nonprotein material of food value, sugar, for instance, being an import-14 ant ingredient of panopepton. The composition of several of these meat preparations and meat-juices has already been given on page 95.

Of carbohydrates, sugar is the most concentrated, but, as is well known, it is not easy to digest unless diluted or mixed with other foods. When taken in concentrated form, it is likely to ferment in the stomach and to produce acids that are irritating to that organ.

Malt extracts are given as foods, and some of them also because they contain an amylolytic ferment. As food, they contain carbohydrate not in its most concentrated state, and yet so concentrated as to be somewhat indigestible. As the sugar in malt extract is glucose, it is less indigestible than ordinary syrup, but not more nutritious. It is not so easy of digestion as honey, and is more liable to ferment and is more inclined to satiate or destroy the appetite than a quantity of milk-sugar that is its nutritive equivalent. The amylolytic ferment that some of the malt extracts contain does not make them so useful as digesters as Taka-diastase and some other preparations of diastase are.