unites with the oxygen of the inhaled air in
the body, thus serving as fuel. The water produced is given off in the
respiration through the lungs and as perspiration through the skin.[3]
Calcium is a metal. The table given allows three pounds of calcium;
united with oxygen, calcium forms lime. This with phosphoric acid
makes phosphate of lime, the basis of the bones and teeth, in which
nearly all the calcium of the body is found.

The elements which bear no direct relation to the force production of
the body, but which enter into tissue formation, are chlorine,
sulphur, iron, sodium, potassium, phosphorus, calcium and magnesium.
Bone tissue contains about 50 per cent. of lime phosphate, hence the
need of this substance in the food of a growing infant, in order that
the bones may become firm and strong. Lack of iron salts in the food
impoverishes the coloring matter of the red blood corpuscles on which
they depend for their power of carrying oxygen to the tissues; anaemia
and other disorders of deficient oxidation result. The lack of
sufficient potash salts is a factor in producing scurvy, a condition
aggravated by the use of common salt. A diet of salt meat and starches
may cause it, with absence of fresh fruit and vegetables. Such
illustrations show the need of a well-balanced diet.

In order to understand the value of the various classes of food and
their relation to the body as force producers, tissue builders, etc.,
the following table may prove helpful:--

| | C.H.
| | Combustibles
| Nitrogen. | Calculated as
| | Carbon.
---------------------------------------------+-----------+--------------
Beef, uncooked | 3.00 | 11.00
Roast beef | 3.53 | 17.76
Calf's liver | 3.09 | 15.68
Foie-gras | 2.12 | 65.58
Sheep's kidneys | 2.66 | 12.13
Skate | 3.83 | 12.25
Cod, salted | 5.02 | 16.00
Herring, salted | 3.11 | 23.00
Herring, fresh