Has this physiological solution of the problem of death the virtue attributed to it by Metchnikoff? Is it as optimistic as he thinks it is? The instinct of death supervening at the end of a normal and well-filled cycle will no doubt facilitate to the aged their departure on the great voyage. The wrench will no longer exist for the dead. Will it not exist for those who are left behind? And since the instinct of death can only exist about the time at which death is expected, will the young man and the man of ripened years look with less horror than to-day at the law which cannot be escaped, when they are in full possession of the instinct of life, but warned of the inevitability of death? INDEX OF AUTHORS. Altmann, 258 Anaxagoras, 34 Aquinas, St. Thomas, 3, 19, 248 Aristotle, 3, 15, 18, 143, 146, 307 Armstrong, 295 Atwater, 137 Bacon, vi., 35, 346 Baker, 233 Balbiani, 161, 165, 191, 206-7, 257 Bang, d’Yvor, 179 Barthez, 3, 19, 24 Beclard, 121 Becquerel, 278 Beijerinck, 193 Benoit, 271 Bernard, Claude, vi., 17, 27, 29, 32, 48, 50-4, 107, 109, 112, 119, 148, 150-1, 171, 190-2, 194, 197, 204, 210, 214-218, 220 _et seq._, 310, 318 Bernoulli, John, 35, 73 Bert, Paul, 194 Berthelot, 91, 98, 128-130, 152, 204, 296 Berthollet, 82 Berzelius, 117 Bichat, 3, 6, 20, 22, 27-30, 35, 55, 158, 170, 198, 308 Blumenbach, 46 Boë, Sylvius Le, 35-6 Boerhaave, 35, 147, 245 Bohr, 29-30 Bokorny, 324 Boltzmann, 265 Bonnet, 23, 49 Bordeu, 3, 10, 19, 22, 24, 312 Borelli, 35 Boscovitch, 37, 248 Bose, 264 Bossuet, 11 Bouasse, 73, 264-5 Boullier, 12 Bourdeau, 237, 242 Boussingault, 149 Brandt, 257 Bravais, 282 Brillouin, 264, 273 Brown, 266 _et seq._ Brücke, 44 Büchner, 325 Buffon, 46, 254, 357 Bunge, von, 3, 14 Burdon, Sanderson, 176 Busquet, 175 Bütschli, 161-2, 175 Cabanis, 245, 246 Cailletet, 272 Calkins, 327, 338 Calvert, 271 Candolle, 20 Cardan, 261 Carnot, 72-3, 89, 92 _et seq._, 101, 114, 121 Charpy, 237, 271 Chauffard, 3, 10, 11, 294 Chauveau, 75, 103, 108, 123, 130, 145, 213 Chevreul, 32 Chossat, 152 Cicero, 347, 359 Clausius, 67, 88 Cohn, 191, 252 Cohnheim, 341 Colding, 58 _note_, 90 Colin, 52 Comte, 189-190, 310 Confucius, 309 Coulomb, 76, 264, 273 Crookes, 295, 302 Cuvier, 3, 6, 27-8, 105, 120, 152, 190, 198, 308, 310, 319 D’Alembert, 20, 59 _note_, 90, 92 Dantec, Le, 48, 52, 55 _note_, 110, 148, 173, 198, 201, 203, 213, 216, 220, 223 _et seq._, 231, 246, 261, 285, 296, 340 D’Arsonval, 126 Darwin, 3, 46, 167, 258, 354 Dastre, A., 192, 198 _note_ Davy, Sir Humphry, 61, 80 Delafosse, 282 Delage, 208 Demange, 349 Democritus, 34, 146 Descartes, 3, 9, 35, 37, 40, 73, 91, 98 Despretz, 126 Diderot, 245, 246 Drechsel, 183 Dressel, 20