§1] 



UPON THE RATE OF GROWTH 



297 



It would be valuable to know the relative number of atoms 

 of each of the metalloids and metals named in the preceding 

 table. This may be determined in the following way : Find 

 the proportion by weight of each metallic radical (excluding 

 the oxygen) in the entire ash and divide this percentage by the 

 molecular weight of the metal. The varying weights of the 

 elements are thus eliminated, and a set of numbers which indi- 

 cate relative abundance of atoms is obtained. We multiply 

 these small fractions by 1000 for convenience. The results 

 are as follows : — 



TABLE XXVJI 



These examples may suffice to show how diverse is the com- 

 position of different organisms and how diverse therefore must 

 be their requirements in the way of food to build up the adult 

 body. The examples serve also to indicate what are the 

 important elements for organisms. They appear to be the 

 same for animals and plants, and are : — 



*Carbon 

 *Oxygen 

 ♦Hydrogen 

 ♦Nitrogen 



While this list does not pretend to exhaust the elements found 

 in organisms, it contains those which are usually present. 



In the organism the atoms just named are, of course, found 

 in combination. The carbon, oxygen, hydrogen, and nitrogen 

 are contained in the organic matter of the organism — the 



* Those elements whicli are starred (*) are essential to all organisms. 



