Medicines From Nature. by Peggy Thomas. Discusses how we have learned from traditional healers around the world about the medicinal value of substances from nature.
Natural and Synthetic Poisons. by Gail Kay Haines. Describes the poisons that come from animals, plants, bacteria, earth, and water and discusses the science of toxicology and the work of a poison control center.
Your Body's Defenses. by David C. Knight. Describes the body's various natural defenses against diseases and gives hints on how one can reinforce these defenses with rest, proper nutrition, etc.