Hygienic Physiology | Page 4

CRANIUM..............| Two
Temporal (temple) Bones. | | (8 bones.) | Sphenoid Bone. | | | Ethmoid
(sieve-like bone at root of nose). | | |_Occipital Bone (back and base of
skull). | | _ | | | Two Superior Maxillary (upper jaw) Bones. | | | Inferior
Maxillary (lower jaw) Bone. | | | Two Malar (cheek) Bones. | | 2.
FACE.................| Two Lachrymal Bones. | | (14 bones.) | Two
Turbinated (scroll like) Bones, each | | | side of nose. | | | Two Nasal
Bones (Bridge of nose). | | | Vomer (the bone between the nostrils). | |
|_Two Palate Bones. | | _ | | | Hammer. | | 3. EARS.................| Anvil. | |
(6 bones.) |Stirrup. | | II. THE TRUNK (54 bones.) | _ | | Cervical
Vertebræ (seven vertebræ of the | _ | neck). | | 1. SPINAL
COLUMN........| Dorsal Vertebræ (twelve vertebræ of the | | | back). | | |
Lumbar Vertebræ (five vertebræ of the | | |_ loins). | | _ | | | True Ribs. | |
2. RIBS.................|_False Ribs. | | | | 3. STERNUM (breastbone). | | | | 4.
OS HYOIDES (bone at the root of tongue). | | _ | | | Two Innominata. |
|_5. PELVIS...............| Sacrum. | |_Coccyx. | | III. THE LIMBS (124
bones.) | _ | | Clavicle._ | | Shoulder...|_Scapula. | | | | 1. UPPER
LIMBS..........| | Humerus. | | (64 bones.) | Arm........|_Ulna and Radius. |
| | _ | | | | _Eight Wrist or Carpal | | | | Bones._ | | |Hand.......| Five
Metacarpal Bones._ | | |_Phalanges (14 bones). | | _ | | | Femur._ | | |
Leg........| Patella. | | | |_Tibia and Fibula. | | 2. LOWER LIMBS..........|
_ | | (60 bones.) | | Seven Tarsal Bones._ | | Foot.......| Five Metatarsal
Bones._ | |Phalanges (14 bones).
_ | 1. Uses. _ | 2. Composition. | 1. FORM, STRUCTURE, | 3. Structure.
| ETC., OF THE BONES | 4. Growth. | | 5. Repair. THE SKELETON |
|_6. The Joints. | _ | 2. CLASSIFICATION OF | 1. The Head. |_ THE
BONES. | 2. The Trunk. |_3. The Limbs. THE SKELETON.
I. FORM, STRUCTURE, ETC., OF THE BONES.

(See page 269.)
THE SKELETON, or framework of the "House we live in," is
composed of about 200 bones. [Footnote: The precise number varies in
different periods of life. Several which are separated in youth become
united in old age. Thus five of the "false vertebræ" at the base of the
spine early join in one great bone--the sacrum; while four tiny ones
below it often run into a bony mass--the coccyx (Fig. 6); in the child,
the sternum is composed of eight pieces, while in the adult it consists of
only three. While, however, the number of the bones is uncertain, their
relative length is so exact that the length of the entire skeleton, and
thence the height of the man, can be obtained by measuring a single
one of the principal bones. Fossil bones and those found at Pompeii
have the same proportion as our own.]
USES AND FORMS OF THE BONES.--They have three principal
uses: 1. To protect the delicate organs; [Footnote: An organ is a portion
of the body designed for a particular use, called its function. Thus the
heart circulates the blood; the liver produces the bile.] 2. To serve as
levers on which the muscles may act to produce motion; and 3. To
preserve the shape of the body.
Bones differ in form according to the uses they subserve. For
convenience in walking, some are long; for strength and compactness,
some are short and thick; for covering a cavity, some are flat; and for
special purposes, some are irregular. The general form is such as to
combine strength and lightness. For example, all the long bones of the
limbs are round and hollow, thus giving with the same weight a greater
strength, [Footnote: Cut a sheet of foolscap in two pieces. Roll one half
into a compact cylinder, and fold the other into a close, flat strip;
support the ends of each and hang weights in the middle until they bend.
The superior strength of the roll will astonish one unfamiliar with this
mechanical principle. In a rod, the particles break in succession, first
those on the outside, and later those in the center. In a tube, the
particles are all arranged where they resist the first strain. Iron pillars
are therefore cast hollow. Stalks of grass and grain are so light as to
bend before a breath of wind, yet are stiff enough to sustain their load

of seed. Bone has been found by experiment to possess twice the
resisting property of