37. The Distribution Of Ash Compounds In The Animal Body

The bones contain a very large proportion of the ash constituents found in the animal body, the soft parts being poor in mineral salts. Usually the ash makes up between 60 and 70 per cent of bone, and the bony framework is from 6 to 9 per cent of the entire bodies of domestic animals. More than 80 per cent of the ash of bone is calcium phosphate, which is associated with calcium carbonate, calcium fluoride, calcium chloride, and magnesium phosphate.

The bones of all species of animals, including man, show a remarkable similarity of composition, the average of which would not be far from the following: -

The muscular tissue and other soft parts of the animal body contain less than 1 per cent of incombustible bodies. The ash from flesh is mostly phosphoric acid and potash, accompanied by comparatively small amounts of soda, lime, and magnesia and minute quantities of chlorine and iron. Unquestionably, potassium phosphate is the predominating salt in flesh, as calcium phosphate is in bone. The blood contains a variety of mineral substances, the chief of which is sodium chloride, or common salt, although a small amount of iron is present, having a most important function. In the bile, soda is abundant, combined mostly with the peculiar organic acids of this secretion. Chlorine is a constant constituent of the gastric juice, its presence as chlorhydric acid being essential to digestion.

38. Forms In Which The Ash Elements Exist In The Plant Or Animal

As has already been suggested, the mineral elements are combined differently in the ash from what they were in the plant or animal substance before ignition. Because calcium or potassium phosphate is found in plant ash or the ash of animal tissue, it does not follow that such a compound existed in the unburned substance. For instance, the phosphorus in a grain of wheat is com-bined in certain organic compounds such as nucleo-pro-teins and phytin. Sulfur exists in certain proteins. When ignition occurs, there is a rearrangement of the elements, and we find the phosphorus and sulfur present in the ash of the wheat kernel in inorganic salts. It is a mistake, in most cases, to speak of any food material containing the compounds that are found in its ash. Recent investigations have demonstrated the absence of inorganic phosphorus in the cereal grains, unless these have been subjected to fermentation, when inorganic salts of phosphorus may be present.