Religion, and diet, 163 and disease, 205 and future life, 150 and science, 3 and sexuality, 163 Tolstoi’s return to, 223 Renal tubule, invasion of macrophags (figure), 241 Renan, on death, 195 on Jewish belief in future life, 142, 143 on Marcus Aurelius, 174 Renaissance, art of, 14 Reproduction, not cause of death in ephemerids, 275 Reproductive organs, 79 Resignation, in Buddhism, 159 Guyau on, 199 Hartmann’s system of, 187 Marcus Aurelius on, 174 Resurrection, primitive belief in, 140 Réville, on Chinese belief in immortality, 145, 146 _Rhizotrogus_ and light, 36 Richet, on failure of science, 222 Rousseau, on age and love of life, 117 on failure of science, 216 on fear of death, 118 Rovighi, on utility of milk diet, 255 Rückert, on death, 195 Rudimentary organs, in man, 59, 60 Sacrifice, at burials, 140, 141 Saint-Foix, on sacrifice of horses, 141 St. Matthew, on celibacy, 12 Savage, on old age in apes, 233 on social instincts of apes, 105 Schiller, on death, 195 Schopenhauer, and cholera, 120 on death, 121, 179, 288 on immortality, 179 pessimism of, 117, 177, 178, 179, 207 Schottelius, on rearing of germ-free chicks, 249 Science, advance of, 286 Bacon on, 204 destroys faith, 226 failure of, 215, 216, 217, 218, 222, 223 and immortality, 287 and old age, 228 and pessimism, 207, 286 Sclerosis of arteries, 248 in old age, 236, 237, 243, 244 due to poisons, 247 Scotch clergy on man, 12 Seidlitz, on natural morality, 8 Selenka, on fœtus of man and ape, 47 Self-preservation, 113, 275 Seneca, on death, 171 on human existence, 171 on immortality, 170 on nature as a guide, 7, 10 Senile decay action of macrophags, 241 characters of, 235, 238, 239 importance of phagocytes in, 241 Sensibility, specific, of white blood corpuscles, 160 Serum, alteration of properties, 51 anti-diphtheritic, 211 properties of, as guide to affinity, 51 Serums, use of, in old age, 245, 246 Sexuality, early appearance of, 94, 95 in the aged, 98 disharmonies of, 100 Sexual cells, immortality of, 268 soul of, 268 Shakespeare, sorrow and knowledge, 227 Shaving, regarded as degrading, 5 Skeleton, of man and apes, 43 Skin, of man, 62 Skoptsy, and emasculation, 9 Social instincts, 105, 109, 113 Societies, of insects, 294 Socrates, and death, 166, 167 Solidarity, of men, 297 Solomon, sorrow and knowledge, 226 Soul of cells, Haeckel on, 269 of protozoa, 268 of sexual cells, 268 Soured milk, benefits of, 255 Spencer, H., on belief in resurrection, 140 on natural morality, 9 on progress, 291 Spermatozoa, immortality of, 267 in old men, 97 Spinoza, on immortality, 175 Sterility, in human life, 295 in social insects, 294 Stoics, _summum bonum_ of, 6 on future life, 169 Strassburger, on microbes of the intestines, 248