308 MODERN SCIENCE READER 



easy it is to relapse into the ways of our forefathers and 

 let our imaginations run wild. 



ELEMENTS OF PLANTS AND ANIMALS 



Another unsolved problem of chemistry is that presented 

 by the fundamental constituents of plants and animals. 

 No one knows better than the chemist that all living things 

 are ''fearfully and wonderfully made." Plants take ma- 

 terials of various kinds from the air and from the earth, 

 and work them up in proper shape for their growth. In 

 turn, animals take parts of some plants or parts of some 

 animals, and work them up so that they become part and 

 parcel of the animal bodies. Life and growth of plant 

 and animal depend upon this power to convert food into 

 other things that can take their proper places in the body. 

 Chemical change is the beginning of life. But what are 

 these things that are formed within the plant and animal? 

 That is a hard question to answer ; and, indeed, the answer 

 would be confusing. All that need be said is that among 

 these things are the fats, sugar, starch, cellulose, and a 

 group of important compounds called proteids. Besides 

 these, there are innumerable substances found both in 

 plants and animals. Naturally, chemists are interested in 

 these things, and they have given, and are giving, much 

 time to their investigation. It is only through such study 

 that we can hope ever to gain any conception of the 

 changes that are taking place in living things, or of the 

 nature of life in its various forms. 



Of the substances mentioned, the fats are relatively the 

 simplest, and they are, accordingly, pretty well understood. 

 It is interesting to note in passing that the first and the 

 most important chemical investigation in fats was carried 

 out at the beginning of this century by the French chemist 

 Chevreul, who died only a few years ago at the age of 103, 

 having kept in harness to the last. Regarding our knowl- 

 edge of fats, it is safe to say that we know enough about 

 them to be able to see how one could, starting with carbon, 



