MuUer, H. J. (1901- ), 512 



Multiple factors, 482 f. ; in inheritance, 

 492 ff. 



Mumps, 235, 445 



Muscles, 292, 294, 296 ; and calcium con- 

 centration, 124 



Mushrooms, 689; "fairy ring" of, 587 



Musk-ox, 7 



Mussels, 92 



Mutations, 489, 490, 509, 510 ff. 



Myriapods, 693 



Myxedema (mik se de'mo), 306, 312 



Naming, 29 ff. ; binomial, 36 



Natural selection, 466 



Nature, balance of, 579 ff. 



Neanderthal (na an'der tal) man, 51, 52; 

 brain of, 297 



Needs, human, 647 ff., 660 



Negro, 63 



Neon (ne'on), 84 



Nerves, 275 ff., 277, 282, 284; in insects, 

 16; endings of, 217 ; impulse of, 292 



Net-veined leaves, 43 



Neuron (nu'ron), 25, 275 



Neurosis, artificial, 670 ff. 



New Stone Age, 55 



Niacin, 108, 128, 132 



Nicotinic acid, 128, 132 



Night bUndness, 133 



Nitrates, 150 



Nitrogen, in air, 84 ; in protein, 97 ; fixation 

 of, 152 f. 



Nitrogen cycle, 149 ff. 



Nitrous oxide, 659 



Non-communicable diseases, 628 ff. 



Normal distribution, 68 f. 



Normality, 66 ff. 



Norms, 66 ff. 



Nose, lining of, 288 



Nucleus, of cell, 10, 24; of neuron, 275; 

 changes in, 368 



Nutrients, organic, 98 ; sources of, 99 ; de- 

 ficiencies of, 100; energ>- value of, 125 



Nutritive values in shares, 131 



Nymph (nimf), 179 



Occupational diseases, 634 



Odors, 288 ; individual differences in, 64 



Old Stone Age, 55 



Ommatidium, 15 



Omnivores (om'nivorz), 150 



Opium, 659 



Orangutan (6 rang'oo tan), 699 ; appendix 

 of, 175 



Orbicular leaves, 43 



Orchids, 408 



Orders, 39, 688 ff. 



Organisms, 18 ; difference of, from nonliving 

 things, 19 f.; anaerobic, 209; of the 

 past, 450 ff. ; grouping of, 562 f. 



Organs, 18,354; comparison of, 18; graft- 

 ing of, 362 



Osborn, Henry Fairfield (1857-1935), 53 



Osmosis (osmo'sis), 86; in roots, 87, 143; 

 in living things, 87 f . ; and turgor, 88 ; and 

 concentration, 124 ; in leaf, 139 ; in blood 

 vessels, 187; in lungs, 192 



Ostrich, 176 



Otter, 548 



Ova, 377 



Ovary, 305, 307, 314, 377 ; in flowers, 398 ff. 



Ovate leaves, 43 



Oviducts, 380 



Oviparous species, 378 



Ovules, 398, 399, 402 



Oxidation of food materials, 83 



Oxygen, in air, 84; in protein, 97; from 

 photosynthesis, 138 



Oxygen cycle, 149 f. 



Oxyhemoglobin, 205 f. 



Oyster, 388, 695 



Pain, 658 f. 



Pahsade cells, 24, 139, 141 



Palmate leaves, 43 



Pancreas, human, 167, 168; of bird, 173; 



as ductless gland, 303, 305, 307 ; cells of, 



348 

 Parallel-veined leaves, 43 

 Parasites, 177, 370, 614 

 Parathyroid (par a thi'roid) glands, 100, 305, 



306 

 Parents, behavior of, 425 

 Pasteur, Louis (1822-1895), 341 

 Pavlov, Ivan P. (1849-1936), 266 ff., 670 ff. 

 Peas, Mendel's experiments with, 474 ff. 

 Pellagra (p^la'grc), 108, 125, 133 

 Penicillin, 240 

 Peptids, 169 

 Peptones, 168, 169 

 Perennials, 180 



714 



