‘Excellent!’ I cried. ‘Elementary,’ said he.

1. Hydrogen—10%
6. Carbon—18%
7. Nitrogen—3%
8. Oxygen—65%
9. Fluorine—0.01%
11. Sodium—0.1%
12. Magnesium—0.05%
15. Phosphorous—1.2%
16. Sulphur—0.2%
17. Chlorine—0.2%
19. Potassium—0.2%
20. Calcium—1.5%
26. Iron—2.3g to 3g
27. Cobalt—0.05%
29. Copper—0.05%
30. Zinc—0.05%
34. Selenium—0.01%
53. Iodine—0.05%

[% by mass of the more common elements in the average human body]