102 WHAT IS LIFE 



atomic weight 58.97) and nickel (atomic number 28, 

 atomic weight 58.68) have been found present in 

 the human body, especially in the pancreas gland, 

 according to Gabriel Bertaud (director of the 

 biological chemical laboratory of the Pasteur In- 

 stitute, Paris). 



Among the elements named is the element that 

 is the most abundant on the earth's crust, oxygen. 



Hydrogen and oxygen as water form more than 

 two-thirds of the earth's surface, and — as mentioned 

 before — constitute from sixty-five to eighty per 

 cent of the organism. The human embryo, it may 

 be recalled, at an early stage of prenatal existence 

 consists of ninety -four per cent water. 



Nitrogen and oxygen are the chief constituents 

 of the atmosphere — the air (a mixture of gases) con- 

 sists of seventy-eight per cent (in volume) of nitro- 

 gen, and twenty-one per cent of oxygen, and small 

 amounts of argon, helium, and other gases. 



Carbon, though predominating in organic com- 

 pounds, is relatively rare. 



Sodium, magnesium, potassium, calcium, and 

 iron, are some of the most abundant of elements. 

 Sodium and chlorine (sodium chlorid) are present 

 in sea-water (the ocean, habitat of numerous life- 

 forms) to the amount of nearly three per cent by 

 weight. 



