Arrhenius, Svante (1859-1927), 152 



Arsenic, 232 



Arteries, 189 



Arthropods (ar'thro podz), frontispiece, 693 ; 



food tube of, 173 ; blood of, 207 

 Artichoke, 253 

 Ascorbic acid, 108, 109, 132 

 Assimilation, 19, 83 ; by cells, 343 

 Associative neurons, 275 

 Asthma, 242, 371 

 Athlete's foot, 614 

 Atmosphere, composition of, 83, 84 

 Atropin (at'ro pin), 231 

 Attitudes, 318, 332 f. 

 Augustine, 447 

 Auricle (6'ri k'l), 190, 191 

 Autonomic (6 to nom'ik) nervous system, 



294 fif. 

 Auxins (ok'sinz), 258 ff. 

 Aves (a'vez), frontispieces, 696 f. 

 Aviation and circulation, 196, 207 

 Axis, nerve, 276 ff. 

 Axon (ak'son), 25, 275 f. 



Bacillus colt, 639 



Backbone, 46 



Bacteria, 24, 25, 36, 688 ; on alfalfa roots, 



152; and digestion, 164; coccus group of, 



242 ; spores of, 371 ; as cause of disease, 



612 ; type of, 613 

 Bacteriophage (bak ter'i o faj), 445 

 Baer, Karl E. von (1792-1876), 356 

 Balance of nature, 579 ff. ; disturbance of, 



582 fif. 

 Balancing organs, 285, 286, 287 

 Banting, Frederick G. (1891-1941), 312 

 Barberry, 595 

 Barnacle (bar'no k'l), 92 

 Barriers, 461 

 Basal metabolism, 118 fif. 

 Basidium, 689 

 Bast, 144, 147 



Bateson, William T. (1861-1926), 482 

 Batrachia {ha tra'kic), frontispiece 

 Bats, 698 

 Beaks, 178 

 Bear, 177 

 Bedbug, 177 



Beetle, calosoma, 594, 596 

 Begonia, regeneration in, 231 

 Behring, Emil von (1854-1917), 237, 240 



"Bends", 207 



Beriberi (ber'i ber'i), 104 ff., 125 

 Bernard, Claude (1813-1878), 302 

 Best, Charles H. (1899- ), 312 

 Biennials, 180 

 Bilateral symmetry, 13, 14 

 Bile, 168, 189; and vitamin K, 132 

 Binomial nomenclature, 36 

 Biogenetic law, 356 

 Biology, 4 ; kinds of, 6 f. 

 Birds, differences between, 30 ; digestive 

 system of, 173; size of, 176; beaks of, 

 178; migration of, 179, 181; breathing 

 of, 21 1 ; tropisms of, 260 ; pollination by, 

 408; development of, 421; destruction 

 of, 584 ; protection of, 586 ; classification 

 of, 696 f. 

 Bison, 7, 588 

 Bladder, 219 

 Blended inheritance, 482 

 "Blind staggers", 102, 103 

 Blood, clotting of, 108 ; corpuscles of, 186 fif. ; 

 circulation of, 189 ff. ; changes in, 192 ff. ; 

 types of, 197 ; of arthropods, 207 ; reac- 

 tions of serum of, 240 ff. 

 Blood banks, 197 

 Blood count, 188 

 "Blood-poisoning", 617 

 Blood vessels, in insect, 16; human, 189 

 "Blue baby", 192 

 Blueberries, 498 



Body, plan of mammal, 13, 48 ; plan of in- 

 sect, 14; surface of, 117 

 Boll weevil, 653, 655 

 Bones, cells of, 25, 348 ; of vertebrates, 48, 



100 ; defective formation of, 98 

 Boron, 103 



Botulism (bot'uliz'm), 237 

 Boys, gain in weight by, 115 ; basal metabo- 

 lism of, 118 ff. 

 Brahman cattle, 7 ; in breeding, 496 

 Brain, human, 50, 51 ; of vertebrates, 278 ff. ; 

 and reflexes, 282 ; areas of, 283 ; size of, 

 297 ; ceUs of, 348 

 Bran, 125 



Bread, requirements for, 125 

 Breathing, in man, 204 ff. ; in vertebrates, 



209 ff. ; rate of, 296 

 Breathing tubes, in insects, 16 

 Breeding, for immunity, 496 ; practical, 

 497 £.; problems of 498 ff. 



706 



