The science of life : fully illustrated in tone and line and including many diagrams

THE GOMPLEX BODY-MACHINE AND HOW IT WORKS

and hand are worked by fifty-eight different muscles working on thirty-two separate bones (three long ones and the rest in the wrist and hand)—counting the big muscles that go to the shoulder-blade, ribs, and collar-bone. The face is provided just under the skin with the thin slips of muscle that move the features and produce various expressions. Anatomists distinguish thirtyone of these muscles. At the sides of the head there are the eight muscles that move the jaw. Below are the complex muscles of the throat, tongue and voice-box, and occasionally we meet gifted individuals who have extra head muscles—thin films over the domed top of the skull by means of which they can waggle their scalp, delicate strips that allow them io twitch their ears. The neck is mostly muscle ; it is purely and simply an anatomical device which allows the head to be turned, raised, or lowered without moving the trunk. (A frog has no neck; if a frog wants to snap at an insect

\\_ Skull (Cranium)

Collar-bone © |

(Clavicle) Backbone (Vertebral Column y)

Shoulder-blade (Scapula)

i Hip-Girdle a (Pelvis)

; Thigh-bone (Fernur)

ae Breast-bone BY (Sternum)

he has to turn his whole body until his mouth is pointing in the right direction. A dog or a man, on the other hand, can turn his eyes and mouth in a number of directions without moving his body.) In the shoulder and chest there are great muscles that bind the arms to the trunk and move the shoulder joint in various ways; in the hips and buttocks there are others that bind the legs to the trunk, moving the hip-joint and supporting the whole weight of the body.

unning over the ribs there is the clothing of muscles that produces the rhythmic swell and ebb of our chests ; and wrapping round the abdomen, just below the skin, is another (three-ply) muscular sheet. These are some of the more important muscles. But in the small space at our disposal we can give no adequate idea of the full complexity of the system. ‘The medical student who is studying “‘myology,” as it is called, has to familiarize himself with some two hundred. names, and since most of these are paired

Skull (Cramum)

Backbone (Vertebral Column)

Collar-bone . (Clavicle)

. | Shoulder-blade pr (Scapula)

Breast-bone (Sternum)

Hip Girdle! (Pelvis)

Thigh-bone a

(Femur) \ \

les Knee-eapeeeo ‘

(Patella) i

Fig. 4. The human skeleton from the back, from the front, and from the side.