5 2 4 



ELEMENTARY BIOLOGY 



Nest of bluebird, 370 



Nests, 334, 371 



Nettle, 347 



Nettling cells, 373 



Neurons, see Nerves 



Newt, development of, 282 



Nicotine, 163 



Nictitating membrane, 234 



Nitrates, 60 



Nitrogen, and bacteria, 62 ; utilization 



of atmosphere, 63 ; and war, 64 

 Nitrogen cycle, 59, 60, 61 

 Nitrogen problem, 61 

 Nitrogenous wastes, 90 

 Nose as sense organ, 227 

 Nosebleed, 192 

 Nose-breathing, 150 

 Nucleus, cell, 23, 296 ff., 303 ; division 



of, 457, 458, 459 

 Nutrition, 260 

 Nutritive ratio, 97, 100, 103 

 Nuts, 317 



Occupational dangers, 158, 235-236 

 Occupations, and air, 156; and diet, 



101 ; and dust, 158-162 ; regulation 



of, 122-124, 213 ff., 216, 395 

 Odors, 202 



QEsophagus, see Esophagus 

 Oleomargarine as butter substitute, 



123 



Ommatidium, 232 

 One-celled animals, 24 

 One-celled plants, 75-77 

 Oosphere, 299, 458 

 Ophthalmia neonatorum, 237 

 Opossum, 335 

 Opsonins, 198 

 Orchids, 308, 312-313 

 Organic, 16, 51, 53, 176 

 Organism, 15, 16, .24; how it learns, 



245; origin, 19, 291 ff. 

 Organs, 15; origin of, 276 

 Osmosis, 40-41, 76, 78, 79, 80, 144 ff., 



149, 174 ff., 180-181, 188, 201 ff., 



260 



Ovary, 301, 302, 303 

 Overpopulation, 472 

 Ovules, 301, 324 

 Oxid, 13 

 Oxidation, 13, 59; in organisms, 13, 29, 



' 5^52, 55, 57,53, 59.132, M3 **, 261 

 Oxygen, 12, 52; in energesis, 143, 



144; in photosynthesis, 54 

 Oxygen cycle, 59 



Palate, no 



Palisade cells, 23, 70 



Pancreas, 82, 85, 86, 188 



Paper wasp, 369 



Parallelism in development, 277, 278, 

 467 



Paramecium, 224 ff. ; conjugation in, 

 296 



Parasites, 410; alternation of genera- 

 tions in, 326; in food, 112 



Parasitic diseases of animals, 420 



Parasitic relations, 341 ff. 



Parasitism, 342 



Parent, dependence of offspring on, 



33 2 



Pasteur, Louis, 133, 386 



Pasteurization, 391 



Patent medicines, 256, 257 



Pawlow, Professor I. P., experiments 

 on digestion, 110 



Pedicel, 70 



Pellagra, 109; relation to diet, 510 



Pepsin, 83 



Peptones, 83 



Peristalsis, 85 



Perspiration, 204 



Petals, 303 



Pfltiger, Eduard F. W., experiments 

 on breathing, 143 



Phagocytes, 182 



Pharynx, 82 



Phloem, 79, 174, 176 



Photosynthesis, 53-56, 59, 73, 378, 477 



Phototropism, 38, 230 



Physic, 119 



Physical changes, 7 



Physiological variation, 438, 439 



Physiology, 15 



Pickling and bacteria, 397 



Piddock, 368, 370 



Pigments, 202, 203, 287 ; and food, 

 354; and light, 288, 351, 352; and 

 temperature, 353; protective, 351 



Piltdown skull, 494 



Pisces, 485 



Pistil, 300, 478 



Pith, in root, 43 ; in stem, 1 75 



Pithecanthropus erectus, 493, 495, 496 



Plague, 506, 510 



Plants, chemical composition of, 31 ; 

 classification of, 478; compared 

 with animals, 19; conducting sys- 

 tem of, 174 ff. ; desert, 359 ; genea- 

 logical tree of plant life, 479 ; hairs 

 of, 347 ; heredity in, 444 ; infancy 



