SALTS. 



85 



(Fig. 80). The flexible condition of the bones may be artificially 

 produced by putting a long bone, like the fibula, into a jar contain- 

 ing dilute hydrochloric acid. The acid dissolves the inorganic salts, 

 and, although in appearance the bone is much the same as before, 

 it will now be found so flexible as to permit its being tied in a 

 knot (Fig. 81). In the blood, calcium phos- 

 phate, which is insoluble in alkaline fluids, is 

 held in solution by the albuminous constituents. 

 Were these withdrawn the calcium phosphate 

 would at once be rendered insoluble, and would 

 be precipitated. 



Source of Calcium Phosphate. Calcium 

 phosphate is an important ingredient of the 

 animal and vegetable food of man. It is 

 contained in flesh, in eggs, in milk, in wheat, 

 in oats, in rice, in peas, in beans, in potatoes, 

 in apples, in cherries, and in some other ali- 

 mentary substances. Its presence in milk 

 needs especial comment. As has been stated, 

 during early life calcium phosphate is in the 

 bones in small amount. The milk, upon 

 which the growing child relies for its nour- 

 ishment, supplies the necessary amount of 

 this salt to give the bones their firmness and 

 rigidity. From this statement it will be seen 

 that the adulteration of milk with water, even 

 though the water is pure, may be of great in- 

 jury to the child. To obtain the necessary 

 amount of calcium phosphate a certain amount 

 of milk must be taken. If half this amount 

 is water, the quantity of the lime-salt present 

 will be but one-half of what it should be, and 

 the child is consequently defrauded. Of 

 course, if impure water is used in the adul- 

 teration, there is the additional danger of 

 introducing the germs of disease with the 

 milk. 



A venues of Discharge. A very small 

 amount of calcium phosphate is discharged 

 from the body a fact which shows its permanent character. It 

 is discharged in the urine, in the feces, and in the perspiration. 



Calcium Carbonate (CaCO 3 ). This salt exists in the bones to 

 the amount of about 300 grams, in the teeth, in the blood, in 

 lymph, in chyle, in the saliva, and sometimes in the urine. Like 

 calcium phosphate, with which it is usually associated, it is insolu- 

 ble in water ; and when it exists in solution its solubility is due 

 either to alkaline chlorids or to free carbonic acid. 



FIG. 81. Bone tied 

 in knot. 



