Periods, geologic, 451 



Peristalsis (per i stal'sis), 168, 219 



Perspiration, 217 



Peruvian bark, 6 



Petals, 401, 402 



Petioles, 140 



Phagocytes (fag'oslts), 188 



Pharynx (far'ingks), 166, 205 



Phloem (flo'em), 144, 145, 147 



Phosphorus, 123 ; in protein, 97 ; poisoning 

 by, 231 



Photosynthesis, 138 flf. 



Phototropism, 256 



Phyla (fi'lc), 38, 688 flf. 



Ph^'lloquinone, 132 



Physical differences, 61 f. 



Pigeon, beriberi in, 104; brain of, 281 



Pigmentation in guinea pigs, 479 



Pigments, 63, 216 



Piltdown man, 51, 52 ; brain of, 297 



Pinchot, Gifford (1865- ), 91 



Pineal body, 305, 307, 308 



Pinnate leaves, 43 



Pisces (pis'ez), frontispiece, 698 f. 



Pistil, 398 



Pith, 146, 147 



Pithecanthropus (pith'e kan thro'pws) erec- 

 tus, 51, 515 ; brain of, 297 



Pituitary (pi tu'i tar i), 305, 306, 308, 310, 

 314 



Placenta (plo sen' to), 380, 423, 697 



Planarians, 228, 692 



Plants, parts of, 11 f.; activities of, 17; 

 cells of, 24 ; classification of, 40, 688 ff. ; 

 cultivation of young, 83 ; wastes from, 

 215, 216; storage in, 215; adaptive 

 movements of, 255 ff. ; alternation of 

 generations in, 383 ff., 412 ; reproduction 

 in flowering, 398 f. ; poUination of, 406 ff. ; 

 scattering seeds by, 409 ff. ; heredity in, 

 480 ; breeding of, 496 ff. ; struggle of, 

 540 ff. 



Plasma, 186; reserves of, 197 



Plasmodium, 371 



Plasmolysis (plaz mol'i sis), 87 



Platelets, 186, 187 



Plover, golden, 179 



Plowing, downhill, 154 



Plumule, 415 



Pneumonia, 242, 243 



Poisons, 230 ff. 



Polled cattle, 498 



PoUen, 14, 400, 401, 403, 404, 406 ff. 



Pollination, 406 ff. 



Polyneuritis (pol i nu ri'tis), 104 ff. 



Polyps, 382, 384 



Poppy, 12 



Population, economic elements of, 648 



Porifera, frontispiece, 692 



Portal vein, 191 



Potassium, 100; and heart action, 124 



Potato beetle, Colorado, 655 



Poverty and sickness, 607 ff. 



Prairie, flora and fauna of, 78 



Precipitin (pre sip'i tin), 241 



Predatory animals, 175 



Preformation theory, 346 f. 



Priestley, Joseph (1733-1804), 659 



Primates (prima'tez), frontispiece, 46, 699; 

 brains of, 51, 279, 297 



Proliferation, 228 



Propagation, vegetative, 362, 372 ; artificial, 

 373 



Proteins, 96 f. ; body use of, 123 ; energy 

 value of, 125 ; test for, 183 



Proteoses, 169 



Protoplasm (pro'to plaz'm), 22 ff. ; funda- 

 mental nature of, 25 f . ; streaming of, 26 ; 

 water in, 80 ff. ; food and, 96 ff. ; builders 

 of, 96 f. ; protein in, 97 ; action of, 97 f. ; 

 metabolism, 114; effect of foreign sub- 

 stances upon, 232 ff. ; variations in, 346 



Protozoa (pro to zo'o), frontispiece, 274, 370, 

 691 f . ; parasitic, 614 



Pseudop)odia (su do po'di a), 24 



Pteridophytes (ter'i do fits), frontispiece, 690 



Pulmonary artery, 191 



Pulse rate, 296 



Pupa (pu'po), 180 



Purkinje, Evangelista (1787-1869), 22 



Pus, 188 



Quadruplets, 360 

 Quick-grass, 12 

 Quinin (kwi'nin), 231 

 Quintuplets, 360, 361 



Rabbits, 589 



Rabies (ra'biez), 614 



Races, 63, 516 f.; and susceptibility, 244; 



superiority in, 520 f . 

 Radiant energ>', 138 



715 



