Sanitation and physiology; being primer of sanitation and human physiology in one volume by Ritchie John W. (John Woodside) 1871-1943

Author:Ritchie, John W. (John Woodside), 1871-1943
Language: eng
Format: epub, pdf
Tags: Physiology, Hygiene
Publisher: Yonkers-on-Hudson, N.Y., World book company
Published: 1920-03-25T05:00:00+00:00

THE MUSCLES

65

bands and loops, which hold the tendons down close to the bones. You can learn the necessity for these ligaments by an experiment, and the same experiment will teach you something about tendons.

Tie a piece of string about the tip of the first or second finger. Run the string back along the front of the finger, across the palm, and up the wrist to the forearm. This string is to represent a tendon. Now get one of your schoolmates to tie strings around your finger, hand, and wrist, as you see in Figure 38. These strings represent the ligaments which hold the tendons in place. From up on the forearm pull on the cord which represents the tendon. What effect has it on the finger and hand? Cut the cords which represent the hgaments, and pull on the cord representing the tendon as before. Does,the cord follow the curves of the fingers and hand, and lie down flat along the bones? What difficulty would we have in the hand if the tendons were not tied down to the bones? Now turn the string about and run it down the back of the finger and hand, and note how a tendon pulling on the back of the finger will open it.

From this experiment you will understand the use of the ligaments in the hand and wrist; you will also realize that without the ligaments around the ankles, the tendons would rise and run straight from the toes to the muscles below the knees; and that all through the body it is very necessary for the tendons to be tied down close to the skeleton.

Constant Contraction of Muscles. Lay the back of your hand on the desk, stiffen your arm at the elbow, and bear down on the desk. Now feel the muscle on the back of your Fig, 38. illustrating how a tet*

Ti. • 1 J J don bends a finger.

upper arm. It is hard and con ^

tracted. It is keeping your arm from bending by pulling on

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