18. In Animals

We are not ignorant of the proportions of the chemical elements in the bodies of our larger animals, including man. Lawes and Gilbert, of England, and the Maine Experiment Station, in this country, have made analyses of the entire bodies, or nearly so, of steers and other domestic animals. These results, combined with our knowledge of the constitution of the compounds of the animal tissues, enable us to calculate very closely the proportions of carbon and other elements in the entire body of man and bovines: -

As the proportion of carbon is much larger in the fats than in the other compounds of the animal body, it is easy to see that the ultimate composition of the ox would vary with his condition, whether lean or very fat. The figures given suffice to show, however, that animals, like plants, contain much more of carbon than of any other element, and that the quantities of the remaining elements stand in the same order in the plant and in the animal, the striking differences being the greater proportion of oxygen in the former and of carbon and nitrogen in the latter. The plant and animal are alike, therefore, in consisting chiefly of those elements which are derived from air and water. Carbon, oxygen, and hydrogen constitute from 83 to 86 per cent of the bodies of fat oxen and steers, raw materials which nature supplies without cost, leaving less than one-sixth of the animal body to be built from elements derived from the soil that have, in part, a commercial value for crop production, which is the fundamental consideration in the production of human food.

19. Ash Elements In Animal Body

In order to compare the plant and animal, it is desirable to consider the elements found in the ash or mineral portion of the animal body. We will return for this information to the analysis of a fat ox made by Lawes and Gilbert. These investigators found that the ash, constituting 8.8 per cent of the dry substance of the entire body, was made up as follows, the mineral or inorganic constituents of the human body being given for comparison: -

Of the elements other than oxygen which appear in the ash, phosphorus and calcium take a leading place as to quantity, although sulfur, potassium, and sodium are essential, even if present in relatively small amounts.