According to Chambers, the average adult at ordinary labour obtains enough food in a day if he eats one pound of meat and two pounds of bread or its equivalent, provided no peculiarities of size, health, or climate are to be accounted for.

The average percentage of water in bread is 37 per cent; in cooked meat, 54 per cent; in vegetables, 70 per cent or more (Letheby).

"Assuming the food average as 23 water-free ounces daily and the mean body weight 150 pounds, the body receives 1/105 of its own weight in water-free solids. The range in different persons is 1/80 to 1/120 of the body weight" (Parkes).

This problem may be differently stated, reckoning in the water with the solid food as follows:

A robust man weighing 144 pounds may consume 1/24 of his body weight, or 6 pounds, in nourishment per diem, divided as follows:

Inorganic food - i. e., water and salts - 3.5 pounds.

Organic food (animal food, 1 pound; vegetable food, 1.5 pound), 2.5 pounds.

It is usually better, unless active exercise is being taken, to eat a little less meat and more vegetable food, as previously stated, and to drink a little more fluid.

The average amount of dry food by weight required for breakfast may be put at 8 ounces, for luncheon 6 ounces, for dinner 9 ounces. The "middle diet" at Guy's Hospital, which is supplied to the majority of the patients, furnishes 29.5 ounces of solid food per diem in addition to liquids. Of course such persons are taking no active exercise. This is equivalent to 17 ounces of dry or water-free food. It consists of 4 ounces of meat (cooked), 12 ounces of bread, 8 ounces of potatoes, 1 ounce of butter, 0.75 ounce of sugar, 0.25 ounce of tea, and 2.5 ounces of milk.

Nitrogenous material should constitute "one fifth of the water-free food, or from 4 to 5 ounces for active life. The ordinary meat rations for soldiers is 12 ounces per diem, of which 20 per cent, or 2.4 ounces, is deducted for waste of bone, tendon, etc. For inactive life, from 3 to 3.5 ounces" (Pavy). This diet will completely replace the nitrogen eliminated from the body. "Two pounds of bread and three fourths of a pound of uncooked beef contain as nearly as possible the right proportion of carbon and nitrogen." This makes 44 ounces of solid food. Water-free meat contains about 0.20 per cent nitrogen.

Fat added to the daily diet in the proportion of about one ounce of butter not only supplies necessary force and tissue elements, but acts favourably in promoting the proper assimilation of the other classes of food and diminishing to a great extent the wear and tear of the tissues. With active work, especially in a cold atmosphere, more than double this amount is consumed with advantage, and even 2.5 ounces form an average allowance for many classes of workmen.

The carbohydrates are required in quantities between 14 and 22 ounces, their main use being to convey energy for heat and mechanical work. 21

The quantity of salts required for daily use varies from 0.5 to 1 1/12 ounce. This quantity is less affected by conditions of temperature and exercise than are other food constituents. Chaumont estimates that a man of 150 pounds can do an average day's work upon a diet of albuminoids, 4.5 ounces; fats, 3.75 ounces; carbohydrates, 18 ounces; and salts, 1 1/12 ounce. These estimates are of water-free constituents.

One of the best means of determining the proper amount of food to sustain a man in good health is derived from a study of the experiences of arctic explorers. Their men are subjected to great hardships and feats of endurance, as well as to intense cold. From the nature of the expeditions no superfluous food can be carried, and yet the chief factor in success is the maintenance of good bodily vigour. For these reasons the rations for arctic travellers have been most carefully established, and a brief review of them will throw much light upon this interesting subject.

The Peary expedition to the north pole in 1887 used 19 ounces of solid food as the ration for the sledging expedition, but this soon proved to be inadequate in the cold of the arctic regions. Dr. Ray used 29 ounces, which also proved insufficient, and later 34 ounces of solid food. Various other expeditions have used 32 ounces of solid food, consisting wholly of pemmican, which has been sufficient.

Molintock, another arctic sledge traveller, used 40 to 48 ounces of food daily. Captain Neary's expedition used 38 ounces of solid food, proportioned as follows: Meat, 20 ounces; biscuits, 14 ounces; potatoes, 2 ounces; sugar, 2 ounces. To this were added chocolate, 1 ounce; rum, 2 ounces; and 1.5 ounce each of tea and tobacco with condiments, making in all 44 ounces of supplies.

De Long quotes from the physician to his arctic expedition that "alcohol proves a great advantage, keeps off the craving for food, preventing gnawing at the stomach, and has kept up the strength of the men as given - 3 ounces per day." (This was during starvation, but, as stated on p. 236, alcohol is injurious to the maintenance of robust health in cold climates).

While performing active exercise in the cold a diet of 1.5 pound of stewed deer's meat did not prevent hunger, but 1.5 pound of pemmican per diem, with one half ounce of tea and one half ounce of Liebig's extract of meat, supported life for some time. On leaving the ship and starting on their long sledge expedition, the following daily ration was allowed each man by Lieutenant De Long:

Breakfast

Pemmican.............................................. 4 ounces.

Ham................................................. 1 ounce.

Bread.................................................. 3 " pieces".

Coffee.................................................. 2 ounces.

Sugar.................................................. 2/8 ounce.

Dinner

Pemmican.............................................. 8 ounces.

Liebig's extract......................................... 1 ounce.

Tea................................................... "

Sugar.................................................. 2/3 "

Supper

Pemmican.............................................. 4 ounces.

Tongue................................................ 1 ounce.

Tea.................................................... "

Sugar..................................................2/8 "

Lime juice.............................................. 1 "

Bread.................................................. 4 ounces.