Saccharine substances, 60 Saliva, 86 Importance of, 88 Secretion of, 86 Salivary glands, 86, 87 {269} Salt, Common, 55 Importance of, 56 Sclerotic coat of the eyeball, 204 Sebaceous glands, 44 Secretion of, 45 Semicircular canals, 223 Sensation of pain, 180 Relations of, to pleasure, 181 of temperature, 187 of weight, 188 Modification of, 178 Production of, 177 Variety of, 178 Sense of hearing, 215 sight, 196 smell, 192 taste, 189 touch, 184 Sense, muscular, 188 thermal, 187 Senses, Special, 177 Sensibility, General, 179 Short-sight, 212 Sinews, 27 Sight, Sense of, 196 Organs of, 198 Skeleton, 19 Skin, 41 Structure of, 41 Skull, 19 Uses of the, 19 Sleep, Necessity for, 38 Amount required, 39 Small intestines, 94 Smell, Sense of, 192 Nerve of, 193 Uses of, 194 Soda in the food, 57 Sound, Production of, 215 Special senses, 177 Spectroscope, 104 Speech, 227 Relation of, to the sense of hearing, 228 Sphygmograph, 116 Spinal column, 21 Spinal cord, 155 Decussation of the, 164 Direction of fibres in, 164 Functions of the, 162 Nerves of, 156 Reflex action of, 165 Spontaneous combustion, 145 Stapes, 220 Starch, 61 Its change into sugar, 61 Different kinds, 61 Effect of boiling, 61 Microscopic appearance, 61 Stimulating substances, 62 Stomach, 90, 92 Digestion, 93 Movements of, 92 Secretion of, 92 St.