| Carbon. | Nitrogen. | |||
| 15,000 grains of bread (rather more than 2 pounds) contains | 4,500 | grs. | 150 | grs. |
| 5,000 grains of meat (about ¾ pounds) contains | 500 | 150 | ||
| 5,000 | 300 | |||
So that ¾ pounds meat and 2 pounds of bread, or its equivalent, would supply the needful carbon and nitrogen with but little waste.
From all these facts it will be plain that a mixed diet is the best and most economical for man; and the result of experience entirely coincides with what might have been anticipated on theoretical grounds only.
The quality and quantity of foods to be taken depends largely upon their digestibility.
The quantity of food necessary for a healthy man taking free exercise in the open air is as follows:
| Meat | 16 | ounces or | 1 | pound avoir. | ||
| Bread and all other carbohydrates, | 19 | ounces,, or,, | 1 | .19 | pound,, avoir.,, | |
| Fat, butter, | 3 | ½ | ounces,, or,, | 0 | .22 | pound,, avoir.,, |
| Water | 52 | ounces,, or,, | 3 | .38 | pound,, avoir.,, |
The quantity and quality of food taken into the system every twenty-four hours, should depend upon the amount and kind of labor done, whether muscular or nervous, whether sitting or not, inactive or active, whether indoors or out of doors; upon the kind of atmosphere we breathe; upon season and climate, etc.; also upon the opportunities we have of throwing off the surplus carbon and nitrogen that the system has been overcrowded with.
These conditions determine the proper variations of the income, since that has to be regulated and corrected by the outcome, and amounts after all to just so much carbon, hydrogen, oxygen, nitrogen, sulphur, phosphorus, saline matter, and water as are contained in the proteids, fats, carbohydrates, salts, and water.
It matters little how food is prepared. The main feature is that the supply is equal to the loss, of good and wholesome quality. Whether the food is manipulated by an artistic $10,000 cook or by a plain, clean housewife, the result is the same. Whether the special sense of taste, the gustatory nerve, has or has not undergone a high course of training and education, the fact remains that all that can be supplied is the necessary material that has been expended by the work and labor done by the muscular and nervous tissues.