Man has always been curious about himself, a curiosity that began centuries ago with an examination of the soul, and that extended in the period of the Renaissance to his anatomy and certain functions such as the circulation of the blood. Chemical science entered the scene in the 18th century, and burst into prominence in the 19th century. As the various chemical elements were discovered, many were found to be present in body fluids and tissues. Organic compounds were recognized; it became known that body heat was produced by the combustion of food; chemical transformations such as the...