So far, our study of organic chemistry has dealt mainly with rather small molecules, containing perhaps as many as 50 to 75 atoms. But there also exist enormous molecules called macromolecules, which contain hundreds of thousands of atoms. Some of these are naturally occurring, and make up classes of compounds that are, quite literally, vital: the polysaccharides starch and cellulose, which provide us with food, clothing, and shelter; proteins, which constitute much of the animal body, hold it together, and run it; and nucleic acids, which control heredity on the molecular level.

Macromolecules can be man-made, too. The first syntheses were aimed at making substitutes for the natural macromolecules, rubber and silk; but a vast technology has grown up that now produces hundreds of substances that have no natural counterparts. Synthetic macromolecular compounds include: elastomers, which have the particular kind of elasticity characteristic of rubber; fibers, long, thin, and threadlike, with the great strength along the fiber that characterizes cotton, wool, and silk; and plastics, which can be extruded as sheets or pipes, painted on surfaces, or molded to form countless objects. We wear these man-made materials, eat and drink from them, sleep between them, sit and stand on them; turn knobs, pull switches, and grasp handles made of them; with their help we hear sounds and see sights remote from us in time and space; we live in houses and move abou

t in vehicles that are increasingly made of them.

We sometimes deplore the resistance to the elements of these seemingly all too immortal materials, and fear that civilization may some day be buried beneath a pile of plastic debris-plastic cigar tips have been found floating in the Sargasso Sea-but with them we can do things never before possible. By use of plastics, blind people can be made to see, and cripples to walk; heart valves can be repaired and arteries patched; damaged tracheas, larynxes, ureters, and even entire hearts can be replaced. These materials protect us against heat and cold, electric shock and fire, rust and decay. As tailor-made solvents, they may soon be used to extract fresh water from the sea. Surely the ingenuity that has produced these substances can devise ways of disposing of the waste they create: the problem is not one of technology, but of sociology and, ultimately, of politics.

Morrison & Boyd, Organic Chemistry, 6^th Edition, Prentice Hall International, 1992.