IRON 43 



acute to cause softening and bending of the bones is known as Osteo- 

 malacia. It is not to be inferred, however, that osteomalacia is always 

 due to deficiency of calcium in the diet. It may be due as indicated 

 above to physiological disturbances or nutritional deficiencies leading- 

 to faulty utilization of the calcium which the dietary affords. 



Calcium is excreted, in part by the kidneys and in part by the 

 intestinal mucosa. A high proportion of soluble phosphates in the 

 diet tends to increase the output of calcium in the feces, probably owing 

 to the formation of calcium phosphate which is insoluble in the alkaline 

 fluids of the intestine. Just as potassium salts increase the output of 

 sodium in the urine, so, and for similar reasons, do magnesium salts 

 increase the output of calcium in the urine. 



IRON. 



Iron is an essential constituent of the red pigment of the blood, 

 Hemoglobin. Since hemoglobin is the carrier of oxygen from the 

 lungs to the tissue-cells, it is obvious that iron in this, if in no other 

 capacity, plays a vital part in the economy of the body, but, in addition 

 to the hemoglobin-iron, iron is also found, and not necessarily asso- 

 ciated with hemoglobin, in other parts of the body. Thus the liver 

 contains about 0.02 per cent, of iron calculated on the basis of the 

 fresh, undried organ washed free from blood. The muscles contain 

 appreciable quantities of iron, especially heart-muscle, which contains 

 about 0.01 per cent, of the fresh, undried weight. In smaller quantities 

 iron is found elsewhere in the body, regularly accompanying Nucleins 

 and Nucleoproteins wherever they are found. 



The iron-content of the adult is subject, like that of other tissue- 

 constituents, to daily losses. Experiments with starving individuals 

 (and it is under conditions of starvation that the body is most economi- 

 cal of its resources) show that the nominal daily loss of iron in the 

 feces is from seven to eight milligrammes, while in addition to this a 

 daily loss of about one milligramme occurs through the kidneys. In 

 all, then, it is probable that about ten milligrammes of iron, or about 

 one three-hundredth of the total hemoglobin-iron in the body is lost 

 per day. This loss must be replaced from the diet. 



Under certain pathological conditions, or conditions of malnutrition, 

 a loss of hemoglobin occurs from the blood and the patient is said to 

 have become "anemic." This loss of hemoglobin may and on the 

 other hand may not be accompanied by a diminution in the number of 

 red blood-corpuscles. As might be anticipated, the result of this 

 condition is suboxidation in the tissues with consequent symptoms 

 which are sometimes of the severest gravity. These are very well 

 illustrated by the chlorosis, or "green sickness" which very frequently 

 overtakes girls at the age of puberty. From periods of remote antiquity 

 antedating by many centuries our knowledge of the chemical compo- 

 sition and significance of hemoglobin, this disease has been combated 



