"Let us remember that if we get a glimpse of the details of natural phenomena, and of those movements which constitute life, it is not in considering them as a whole, but in analyzing them as far as our limited means will permit. In the vibrations of the globe of air which surrounds our planet, as in the undulations of the ether which fills the immensity of space, it is always by molecules which are intangible for us, put in motion by nature, always by the infinitely little, that she acts in exciting the organs of sense, and she has modeled these organs in a proportion which enables them to partake in the movement which she impresses upon the universe. She can paint with equal facility on a fraction of a line of space on the retina, the grandest landscape or the nervelets of a rose leaf; the celestial vault on which Sirius is but a luminous point, or the sparkling dust of a butterfly's wing; the roar of the tempest, the roll of thunder, the echo of an avalanche, find equal place in the labyrinth whose almost imperceptible cavities seem destined to receive only the most delicate sounds." _ _ | 1. THE TOUCH...| 1. Description of the Organ. | |_2. Its Uses. | _ | 2. THE TASTE...| 1. Description of the Organ. | |_2. Its Uses. | _ | 3. THE SMELL...| 1. Description of the Organ. | |_2. Its Uses. | _ _ | | 1. Description of the | a. _External Ear._ | | Organ...............| b. _Middle Ear._ | 4. THE HEARING.| |_c. _Internal Ear._ | | 2. How we Hear | |_3. Hygiene of the Ear. | _ | | 1. Description of the Organ. | | 2. Eyelids, and Tears. | | 3. Structure of the Retina. |_5. THE SIGHT...| 4. How we see. | 5. The Use of the Crystalline Lens. | 6. Near and Far Sight. | 7. Color Blindness. |_8. Hygiene of the Eyes. THE SPECIAL SENSES 1. TOUCH. DESCRIPTION.--Touch is sometimes called the "common sense," since its nerves are spread over the whole body. It is most delicate, however, in the point of the tongue and the tips of the fingers. The surface of the cutis is covered with minute, conical projections called _papillæ_ (Fig. 24). [Footnote: In the palm of the hand, where there are at least twelve thousand in a square inch, we can see the fine ridges along which they are arranged.] Each one of these papillæ contains its tiny nerve twigs, which receive the impression and transmit it to the brain, where the perception is produced. USES.--Touch is the first of the senses used by a child. By it we obtain our idea of solidity, and throughout life rectify all other sensations. Thus, when we see anything curious, our first desire is to handle it.