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                               |    1.83   |     21.00
Whiting                                      |    2.41   |      9.00
Mackerel                                     |    3.74   |     19.26
Sole                                         |    1.91   |     12.25
Salmon                                       |    2.09   |     16.00
Carp                                         |    3.49   |     12.10
Oysters                                      |    2.13   |      7.18
Lobster, uncooked                            |    2.93   |     10.96
Eggs                                         |    1.90   |     13.50
Milk (cows’)                                 |    0.66   |      8.00
Cheese (Brie)                                |    2.93   |     35.00
Cheese (Gruyere)                             |    5.00   |     38.00
Cheese (Roquefort)                           |    4.21   |     44.44
Chocolate                                    |    1.52   |     58.00
Wheat (hard Southern, variable average)      |    3.00   |     41.00
Wheat (soft Southern, variable average)      |    1.81   |     39.00
Flour, white (Paris)                         |    1.64   |     38.50
Rye flour                                    |    1.75   |     41.00