Sunflower, 302 ; mutation, 499 



Surface, earth, 521-525 



Surgeon General, 344 



Surgery, appendicitis, 362; and cancer, 361; and 



infection, 331-332; and sulfa' drugs, 334 

 Survival of the fittest, and evolution, 558 

 Susceptible, to disease, 324 

 Suspension. 108 

 Swallowing, 192-193 

 Swarming, of bees, 48, 49 

 Sweat, 239-241 ; glands, 239-240, 240 

 Swiss cheese, 384 

 Symbiosis, 374-375 

 Symbols, of elements, 108-109 

 Symmetry, bilateral, 55; radial, 55 

 Synapse, def., 276; 276, 277; in reflex arc, 278 

 Syphilis, 332-333 



Tables of food values, 172-193 



Tadpoles, 30, 428; changing to frog, 428; and 

 thyroxin, 247-248 



Tail, in embryos, 548 



Tapeworm, 58, 355, 3 55 



Taproot, beet, 148, 149 



Tar pool, 527, 528 



Tarantula, 51 



Taste buds, 280 



Teeth, 192, 203; armadillo, 193; dog, 193; horse, 

 193; human, 193; infected, 364 



Temperature, and bacterial growth, 314; body, 239; 

 def., 168; regulation, 239-241 



Tenderizing, of meat, 383-384 



Tendrils, plant, 301-302; squash, 302 



Tent caterpillar, nest, 393 



Tentacles, jellyfish, 61; octopus, 54 



Terminal branches, of neuron, 275 



Termites, 49; and symbiosis, 374; damage by, 49 



Testis, 421 



Tests for compounds, 110, 116 



Tetanus, 330, 331; bacilli, 320 



Texas cattle, 499 



Thallophytes, classification of, 90 



Thiamin, 179, 180, 183; in common foods, 173 



Thigmotropism, 301-302 



Thistle tube, 122, 123; in diffusion experiment, 123 



Thoracic duct, 221 



Thorax, of grasshopper, 45; of insect, 41 



Thorndike, E. L., and behavior, 291 



Thoroughbred, horse, 493 



Thousand-leggers, 41, 41 



Throwback, def., 474 



Thunder lizard, 537-538 



Thymus gland, 255 



Thyroid gland, 226, 246-250, 247 



Thyroxin, 246, 247, 248-249; efi'ect of, 248 



Ticks, 51 



Time clock, for man, 566, 568 



Timothy, 84 



Tissues, 129-133, 215, 221, 227, 240, 276; culture 

 of, 339-340; origin in embryo, 426; plant, 133, 

 133, 139, 139, 151-153, 152, 153, 153-154, 154; 

 relation to lymph, 221; stomach, 194-195; types, 

 129, 130, 132 



Toads, 31, 31; midwife and eggs, 430 



Tobacco, 87; and health, 365-366; mammoth mu- 

 tation of, 498; mosaic disease of, 340 



Tongue, man, 226; as taste organ, 202-203 



Tonsils, 226; and infection, 364 



Toothache, 204 



Topsoil, 402, 403 



Tourniquet, 215 



Toxln-aulitoxin, and diphtheria, 329 



Toxins, bacteria, 316; diphtheria, 328; and diph- 

 theria susceptibility, 330; malaria, 350-351; tet- 

 anus, 331 



Toxoid, 328-329; for tetanus, 331 



Tracer atoms, 250 



Trachea, 189, 226, 227, 227, 247 



Tracheids, 155 



Trachoma (eye infection) and sulfa drugs, 334 



Transfusions, and blood banks, 211-212 



Translucent, 116 



Transpiration, 159-160 



Transplantation, of bacteria, 314 



Transportation system; earthworm, 57; human, 

 206-225; plant, 148-165 



Trapdoor spider, 51 



Trees, def., 80; cross-section, 156 



Trial and error learning, 290-291 



Trichinosis, 354-355 



Trilobite, 535-536, 535, 536 



Tropisms, 301-304, 305; animal, 265-266, 266 



Trudeau, E. L., and tuberculosis. 337 



Trunk, 154; cross-section of, 156; of tree, 154-155 



Trypsin, 196 



Tsetse fly, 349 



Tube feet, of starfish, 56 



Tube nucleus, 442, 442 



Tuber, def., 449 



Tuberculosis, 321-322; death rate graph, 321; fol- 

 lowing hookworm, 354; and milk supply, 345; 

 statistics of death by, 321-322; vaccine for, 328; 

 and x-ray, 322, 323 



Tubes, in roots, 152; water-conducting, 155 



Tulips, response to temperature, 302; "sleep" move- 

 ments of, 305; structure of flower, 439; vegetative 

 reproduction of, 448 



Tumor, 360-361 



Turgidity, and plant behavior, 304 



Turkey, behavior of bush, 263-265 



Turtles, 30; babies hatching, 429; skeleton, 548 



Twig, horse chestnut, 155 



Twins, fraternal, 514; identical, 514 



2-4-D, 308 



Twort, and bacteriophage, 340 



Tyndall, John, and spontaneous generation, 411- 

 412 



Typhoid, bacteria, 313; and carriers, 347; death 

 rate, 345; fever, 326-327; statistics, 326; and 

 water supply, 344-345 



Typhus, vaccine preparation, 327 



Tyrannosaurus, 537, 538 



Ultramicroscopic, def., 456; genes, 456 

 Ultra-violet light, and germs, 348; and microscopes, 



12; and sunburn, 242; and vitamin D, 181 

 Umbilical cord, 432 

 Undulant fever, and milk supply, 345 

 Unequal division, in yeast, 413-144, 413 

 United Nations, and World Health Organization, 



370 

 United States, Department of Agriculture, 501-502; 



Fish and Wildlife Service, 406; Forest Service, 



402; Public Health Service, 328, 344, 362-364; 



tuberculosis death rate, 321 

 Unlearned behavior, 262-266 

 Uranium, 525 

 Urea, 199; as waste, 237 

 Ureter, 238, 238; of frog, 422 

 Urine, 238; and diabetes, 251 

 "Use and disuse," theory of evolution, 560 

 Uterus, 432, 432 



615 



