Introduce and discuss the indirect effects caused by disease spread and polluted water, including bacterial, viral and fungal effects. View how these indirect factors can affect both plant and animal organisms. Arrive at a workable definition for poor health. Introduce the term toxicology and relate it to toxin and toxicity. Recall the readings in "Silent Spring" which discuss the environmental effects of pesticides and herbicides on human health. Define the term "dose" and relate it to the slow poisoning of fish and birds as discovered by Rachel Carson. Talk about how much of Carson's predictions have come to fruition.