Motor Nerve Cells, ix, 125, 126, 129, 160; connections, 130 (fig.), 131, 147, 148 (fig.) Motor Nerves, at birth, ix, 348 Motor Neurones, xi, 21, 22, 24; development in embryo, 34, 35 Motor Response, defined, xi, 123-4; method of, 26-7; sensation dependent on, 27-8, 43, 63, 66, 74-5, 102-3, 110-11, 118-21, 202-3; to contact and distance senses, ix, 95, 121, 140; violence in emotions, xi, 134 (see also Final Common Path, Reactions, Reflex Actions) Motors, iv, 308-9, vi, 217-63, vii, 367, 373; advantages over engines, 223; air-driven, v, 129-30; alternating-current, vi, 240-63; automatic regulation, 218, 224-9, 232; automobile, v, 156-61; compressed-air effects, 128; compression and non-compression, 157; constant-speed, vi, 231; direct-current, 217-39; direction of revolutions, 56; earliest form, 21; efficiency, 228; efficiency in cold weather, vii, 194; electromagnetic, vi, 95-6; for farm purposes, vii, 223-4, 225-6, 228; heat, Clausius's principle, xvi, 135; individual machine, vii, 52; in household appliances, 74, 78, 83-4, 86; interchangeability with dynamos, iv, 54; multiple cylinder, v, 159; of electric cars, vii, 182-3, 185, 186; of electric locomotives, 196, 200; popular applications of, iv, 10; power, on what dependent, vi, 223; ratings, 192-4; self-regulation of voltage, 226-8; single-cylinder, v, 157; speed variation and constancy, vi, 240-1; starting and starters, 235-9, 250-5, 262-3; synchronous, 241; three-phase system, 206-7; torque of, iv, 309, vi, 224-7; toy, 95-9; voltage generated, 247; water and air-cooled, v, 159-61; waterproof in U. S. Navy, vii, 332 Motor Tractors, v, 214, 215-218, 243 Motor Trucks, v, 214; advantages to farmers, vii, 231; growing use, 195 Motor Type of Men, xi, 155, 157, 158-9 Mott, Valentine, x, 121-2 Motus Peculiaris, ii, 346 Mound Builders, weaving of, xv, 248 (fig.) Mountain-and-Valley Breezes, i, 131, 132, 377 Mountain Goats, xii, 325 Mountain Health Resorts, i, 322 Mountain Lions, xii, 363 Mountain Observatories, ii, 139-51 Mountain Passes, formation of, xiv, 58, 176