600 Useful Science 699

600 Technology 600 General Technology 608 Inventions & Patents 610 Health & Medicine 612 Human Body 612 General Human Body 612.1 Circulatory System - Heart & Blood 612.2 Respiratory System - Lungs 612.3 Digestive System 612.6 Growth & Reproduction 612.7 Human Muscular & Skeletal System 612.8  Human Brain, Spinal Cord & Senses 613 Health 613.2 Nutrition 614 Safety, Emergency Services, & Prevention of Disease 617.6 Dentistry 618.92 Lice 620 Engineering 620 General Engineering 621 Power Sources 621.3 Electricity 621.36 Lasers 621.38 Radar, Telephone, & Television 621.39 Computer Engineering 621.4 Energy 621.4 General Energy 621.4   Wind Energy 621.44   Geothermal Energy 621.47   Solar Energy 621.48   Nuclear Power 621.8 Machines, Wheels 623.8 Ships, Boats, Boating 624 Bridges 625.1 Trains 628.9 Fire Fighting 629.13 Aviation 629.13 General Aviation 629.13   Airplanes 629.13   Helicopters 629.13   Hot Air Balloons 629.13   Zeppelins 629.2 Cars, Motorcycles & Trucks 629.4 Space Travel 629.47 Model Rockets 629.8 Robots 630 Agriculture 631  Farming 635 Gardening 636 Farm Animals & Pets 636.08   Pets 636.089   Veterinary Medicine 636.1   Horses 636.2  Cows 636.3   Sheep 636.5   Chickens 636.6  Birds as Pets 636.7   Dogs 636.8   Cats 637 Eggs 639 Aquariums 640 Home Economics & Cooking 641.3 Chewing Gum 641.3 Chocolate 641.3 Rice 641.5 Recipes & Cookbooks 641.8 Bread 650   Management 652 Codes & Secret Writing 660 Chemical Engineering 670  Manufacturing 674 Wood Products 680 Specific Manufacturing 688 Toys 690 Buildings