Insectivores, 698 



Insects, 14 f., 16, 694 f. ; air-tubes of, 



207 f . ; water-breathing, 209 ; tropisms 



of, 260 ; reproduction of, 381 ; sexual 



dimorphism in, 391 ; pollination by, 408 ; 



and disease, 618 ff. ; damage to crops by, 



655 

 Insulin, 307, 312 f. 

 Interdependence, 652 f. 

 Instincts, 264 ff. 

 Internal secretions, 304 ff . 

 Intestine, 167 ff. ; lining of, 171 ; large, 171 ; 



in bird, 173 ; in fish, 173 ; in lobster, 173 

 Invertebrates, reproduction of, 381 ff. ; 



aquatic, 381 

 Iodine (I'o din), 98; and thyroid, 100, 101 

 Iris, color of, 63 

 Iron, 98, 123 ; in hemoglobin, 102 ; in flour, 



128 

 IrritabiHty, 19 f. 

 Irritants, skin, 637 

 Isles of Langerhans, 307 



James, WiUiam (1842-1910), 527 



Japanese beetle, 595, 655 



Java ape man, 51 



Jaws, 16 



Jellyfish, 32, 692 



Jenner, Edward (1749-1823), 235, 236 



June bug, 352 



Kangaroo, appendix of, 175 



Kelp, 688 



Kenny, Elizabeth, 294 



Kidney, of bird, 173; function of, 195, 



218 ff.; human, 218 

 Koala (ko a'lc) bear, 426 

 Koch, Robert (1843-1910), 612 

 Kripton (krip'ton), 84 



Labor, division of, 529 ff. 



La Brea, 452, 455 



Lacteal (lak'te(il), 171 



Lactic acid, 222 



Lamarck, Jean B. (1744-1829), 464 f., 467 



Lanceolate (lan'se 6 lat) leaves, 43 



Land types of North America, 569 



Larvae (lar've), 179, 180, 263 



Larynx, 100 



Latex tubes, 215 



"Laughing gas", 659 



Laveran, Alphonse (1845-1922), 621 



Lawes, John (1814-1900), 642 



Layering, 370, 373 



Lead, poisoning by, 231 



Leaf, 11, 12; cells of, 24; variety in char- 

 acters of, 43 ; fall of, 91 ; photosynthesis 

 in, 138 ff.; transpiration in, 140; structure 

 of, 141 ; fibrovascular bundles in, 144, 

 145 ; in air and water, 203 ; illumination 

 and growth of, 252 



Learning, 268 f . ; by doing, 667 



Leech, 177 



Leeuwenhoek, Anton van (1632-1723), 21, 

 22 



Legumes (leg'umz), 31, 151 



Lemurs (le'm»rz), 55, 699 



Lens of eye, 15 



Lenticels (len'ti selz), 143, 202 



Lice and disease, 625 



Lichens, 689 



Liebig, Justus von (1803-1873), eA2 



Life, 9 ff. ; preservation of, 20 ; origin of, 

 20 ; characteristics of, 20 ; and water, 78 ; 

 in the past, 437 f., 439 f . ; in space, 440 ; 

 beginnings of, 441 ff. ; from nonliving, 

 443 ff. ; and death, 527 ff. ; distribution 

 of, 534 ff. ; and light, 559 



Life expectancy, 630 



Life span of mammals, 423 



Light, function of, 138 ff. ; and growth, 

 255 f. ; sensitiveness to, 289 f. ; and life, 

 559 



Lime-juice for scurvy, 104 



Linear leaves, 43 



Linkage, and chromosomes, 488 ; in fruit 

 fly, 490 



Linnaeus, Carl (1707-1778), 34, 36, 447 



Lion, teeth of, 177 



Lister, Joseph (1827-1912), 618 



Liver, human, 167, 168; in bird, 173; in 

 fish, 173; and blood corpuscles, 189; 

 cells of, 348 



Liver-fluke, 177, 615 



Liverworts, 689 



Lizard, skin of, 90 ; regeneration, 230 



Lobed leaves, 43 



Lobster, digestive system of, 173 ; regenera- 

 tion in, 229 ; infancy of, 420 



Lockjaw, 233, 237 



Locomotion, means of, 49 



Locust, 350 



712 



