APPENDIX. 



The Chemical Basis of the Human Body. 



OF the sixty-seven known chemical elements no less than seventeen 

 combine, in large or smaller quantities, to form the chemical basis of 

 the animal body. 



The substances which contribute the largest share are the non-metal- 

 lic elements, Oxygen, Carbon, Hydrogen, and Nitrogen oxygen 

 and carbon making up altogether about 85 per cent of the whole. The 

 most abundant of the metallic elements are Calcium, Sodium, and 

 Potassium. 



The following table represents the relative proportion of the various 

 elements. (Marshall. ) 



Fluorine, . . . .08 



Potassium, . . .026 



Iron, 01 



Magnesium, . . .0012 



Silicon, . .0002 

 (Traces of copper, lead, and 

 aluminium), 



100. 



Oxygen, . . .72.0 



Carbon, . . . - . 13 5 

 Hydrogen, . 



Nitrogen, . . .2.5 

 Calcium, . . . 1.3 



Phosphorus, . . .1.15 

 Sulphur, . . . .1476 



Sodium, ... .1 

 Chlorine, . . . .085 



Compounds. Few of these elementary substances occur free or un- 

 combined in the animal body. They are generally united in various 

 numbers, and in variable proportions to form compounds. Traces of 

 uncombined Oxygen and Nitrogen, however, have been found in the 

 blood, and of Hydrogen as well as of Oxygen and Nitrogen in the intes- 

 tinal canal. 



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 is now applied simply to the compounds of the element Car- 

 bon, irrespective of their origin. 



Characteristics of Organic Compounds. A large number of the ani- 

 mal organic compounds are characterized by their complexity. Many 



