154 THE FEEDING OF ANIMALS 



220. Distribution of mineral elements in animal body. 

 The bones carry the greater part of the ash elements. 

 Fresh bones are approximately one-quarter ash. The 

 muscles have between 1 and 2 per cent of ash, and the 

 blood from eight to nine parts in a thousand. The dis- 

 tribution of the mineral elements in the animal body is 

 somewhat as follows: phosphorus and calcium predom- 

 inate in the bones; sodium salts are found largely in the 

 blood, the serums, and lymph; potassium salts exist most 

 abundantly in the blood, muscles, brain, and liver. Iron 

 compounds are found most largely in the blood, lungs, 

 liver, and spleen; and magnesium in the lungs, muscles, 

 and nervous tissue. Sulfur, as has been seen, is asso- 

 ciated with many of the proteins and is found in espec- 

 ially large proportions in hair and horn. 



221. Relation of mineral elements to elimination of 

 waste products. In this respect, iron exercises a particu- 

 larly important function. As has been seen, it is con- 

 tained in the hemoglobin of the red corpuscles. In the 

 lungs, oxygen becomes lightly attached to this hemo- 

 globin and is carried to the various parts of the body 

 where it is used for the oxidation of the organic com- 

 pounds in the food. The red corpuscles seize upon the 

 carbon dioxid which is one of the products of this oxida- 

 tion and carry this to the lungs where it is eliminated. 

 As these oxidation processes furnish the energy for sus- 

 taining the activities of the animal body, it appears that 

 iron is a most important factor in animal metabolism. 



222. Relation of mineral elements to a proper equilib- 

 rium between the acids and bases of the animal body. 

 The cleavage processes which take place hi the use of 

 food compounds give rise to sulphuric and phosphoric 

 acids, and these together with certain organic acids must 



