Please note: This is a companion version & not the original book. Sample Book Insights: #1 The walls of refrigerators are typically insulated with polyurethane foam, which was originally blown with chlorofluorocarbons. The refrigerant was later replaced by hydrofluorocarbons, which contribute to the greenhouse effect. #2 The snake that coiled around a staff is a symbol of healing, and it was originally found in Greece. It may be that snakes have some healing properties because their mouths are vulnerable to damage as they ingest their prey. #3 The workers who built the underwater foundations of the Brooklyn Bridge often experienced excruciating pain when they returned to the surface of the Hudson River. It was caused by decompression sickness, but they referred to it as the bends. #4 The snake that coiled around a staff is a symbol of healing, and it was originally found in Greece. The workers who built the underwater foundations of the Brooklyn Bridge often experienced excruciating pain when they returned to the surface of the Hudson River. It was caused by decompression sickness, but they referred to it as the bends.