1 6 MAN, THE ANIMAL 



potassium, magnesium, calcium, iron, sodium, 

 chlorine, and silicon. These elements are the most 

 numerous in the rocks, water and atmosphere. But 

 the amount of these elements, even those that are 

 essential to life, found in an organism bears no 

 relation to their abundance in nature. 



Nature has taken just these few chemical units 

 and constructed the endless variety found in living 

 things. This fact alone is one to cause us to 

 marvel that man in all of his complexity, adapta- 

 tions and differences can be resolved into this 

 limited number of chemical atoms. All that man 

 does is limited to using just these several atoms 

 combined now into this pattern, now into that and 

 beyond certain combinations he cannot go because 

 he is limited by his chemical constitution. 



Another law thus specifies what inanimate 

 materials unite to form protoplasm. When a 

 biologist refers to this law he usually expresses it 

 as (2), law of the chemical composition of living 

 things, and gives to it the meaning stated under 

 this caption. This law began to be recognized 

 about 1828 with the researches of Wohler, Kolbe, 

 Serthelot and especially Liebig, who first at- 

 tempted a systematic survey of the chemical pro- 

 cesses in living organisms. 



All of these several chemical bodies do not ex- 

 hibit living characteristics except when constituting 

 a part of living protoplasm. We need to keep 



