with oxygen it forms magnesia 14. _Silicon_, a non-metallic 0 0 2 substance. With oxygen it forms silex or silica. It enters into the composition of the teeth and hair 154 0 0 Other elements have been found in the body, as copper and manganese, but these are probably accidental. These elements, when combined together, form a set of compound bodies called “proximate principles,” out of which the tissues and fluids of the body are formed. PROXIMATE PRINCIPLES OF THE HUMAN BODY. lbs. ozs. grs. 1. _Water_, composed of oxygen and 111 0 0 hydrogen gases 2. _Gelatin_, of which the walls of 15 6 0 the cells and many tissues of the body, as the skin and bones, are principally composed 3. _Fat_, which constitutes the 12 0 0 adipose tissue 4. _Phosphate of Lime_, forming the 5 13 0 principal part of the earthy matter of the bones 5. _Fibrin_, forming the muscles and 4 4 0 the clot and globules of the blood 6. _Albumen_, found in the blood and 4 3 0 nerves 7. _Carbonate of Lime_, also entering 1 0 0 into the composition of bone 8. _Chloride of Sodium_, common salt 0 3 376 9. _Fluoride of Calcium_, found in the 0 3 0 bones 10. _Sulphate of Soda_ 0 1 170 11. _Carbonate of Soda_ 0 1 72 12. _Phosphate of Soda_ 0 0 400 13. _Sulphate of Potash_ 0 0 400 14. _Peroxide of Iron_ 0 0 150 15. _Phosphate of Potash_ 0 0 100 16. _Phosphate of Magnesia_ 0 0 75 17. _Chloride of Potassium_ 0 0 10 18. _Silica_ 0 0 3 154 0 0 These compounds, in passing away from the body, form many others, which may be here left out of consideration as not forming a necessary part of the fabric of the human body. None of these constituents of the body remain permanently in the system, and whilst the old particles are being removed new ones are supplied by the food. It is calculated that in this way a quantity of material, equal to the weight of the whole body, is carried away every forty days. So that we may be said to moult or cast away our old body and get a new one every forty days.