THE PHYSICAL BASIS OF LIFE 11 



susception, the power of reproduction, the power of adapta- 

 tion, and specific form and organization. 



1. Chemical Composition 



It is impossible to make an analysis of living matter 

 because the disturbance of its molecular organization by 

 chemical reagents kills it. Therefore our knowledge of its 

 chemical composition has of necessity been derived from a 

 study of dead protoplasm. However, since in the trans- 

 formation from the living to the non-living state there is 

 clearly no loss of weight, it follows that the complete material 

 basis of life is still present for examination. In other words, 

 the death of protoplasm is a result of disorganization. 



Chemical analysis of protoplasm shows that it invariably 

 comprises the elements carbon, oxygen, hydrogen, nitrogen, 

 sulfur, and phosphorus; and usually also chlorine, potassium, 

 sodium, magnesium, calcium, and iron. Occasionally a num- 

 ber of other elements are found normally in the protoplasm 

 of certain parts of various species of animals and plants. 



The average composition of the human body is about as 



follows: 



Oxygen 65.00% 



Carbon 18.00 



Hydrogen 10.00 



Nitrogen 3.00 



Calcium 2.00 



Phosphorus 1.00 



Potassium 0.35 



Sulfur 0.25 



Sodium 0.15 



Chlorine 0.15 



Magnesium 0.05 



Iron 0.004 



Iodine traces 



Fluorine traces 



Silicon.. traces 



