APPENDIX A. 



THE CHEMICAL BASIS OF THE HUMAN BODY. 



Of the sixty-four known chemical elements no less than seventeen have 

 "been found, in larger or smaller quantities, to form the chemical basis of 

 the animal body. 



The substances occurring in largest quantities are the non-metallic ele- 

 ments, Oxygen, Carbon, Hydrogen, and Nitrogen oxygen and carbon 

 making up altogether about 85 per cent, of the whole. The most abun- 

 dant of the metallic elements are Calcium, Sodium, and Potassium. 



The following table represents the relative proportion of the various 

 elements. (Marshall. ) 



Oxygen 72-0 



Carbon ....... 13 '5 



Hydrogen 9*1 



Nitrogen 2 '5 



Calcium 1-3 



Phosphorus 1'15 



Sulphur -1476 



Sodium *1 



Chlorine -085 



Fluorine -08 



Potassium -026 



Iron -01 



Magnesium . . . . -0012 



Silicon -0002 



(Traces of copper, lead, and 

 aluminium) . . . 



100- 



Compounds. The elementary substances above-mentioned seldom 

 occur free or uncombined in the animal body; but are nearly always 

 united among themselves in various numbers, and in variable proportions 

 to form "compounds." Several elements have, however, been detected 

 in small amount free; traces of uncombined Oxygen and Nitrogen have 

 been found in the blood, and of Hydrogen as well as of Oxygen and 

 Nitrogen in the intestinal canal. 



Organic and Inorganic Compounds. It was formerly thought 

 that the more complex compounds built up by the animal or vegetable 

 organism were peculiar, and could not be made artificially by chemists 

 from their elements, and under this idea they were formed into a distinct 

 class, termed organic. This idea has been given up, but the name is still 

 in use, with a different signification. The term organic is now applied 



