endons which bound the space (popliteal) behind
the knee can be distinctly felt when the muscles which bend the knee are
in action. On the outer side note the tendons of the biceps of the leg,
running down to the head of the fibula. On the inside we feel three
tendons of important muscles on the back of the thigh which flex the leg
upon the thigh.

Experiment 29. _To show the ligamentous action of the muscles._
Standing with the back fixed against a wall to steady the pelvis, the
knee can be flexed so as to almost touch the abdomen. Take the same
position and keep the knee rigid. When the heel has been but slightly
raised a sharp pain in the back of the thigh follows any effort to carry
it higher. Flexion of the leg to a right angle, increases the distance
from the lines of insertion on the pelvic bones to the tuberosities of
the tibia by two or three inches--an amount of stretching these muscle
cannot undergo. Hence the knee must be flexed in flexion of the hip.

Experiment 30. A similar experiment may be tried at the wrist. Flex the
wrist with the fingers extended, and again with the fingers in the fist.
The first movement can be carried to 90 degrees, the second only to 30
degrees, or in some persons up to 60 degrees. Making a fist had already
stretched the extensor muscles of the arm, and they can be stretched but
little farther. Hence, needless pain will be avoided by working a stiff
wrist with the parts loose, or the fingers extended, and not with a
clenched fist.

Review Analysis: Important Muscles.

Location.
Name. Chief Function.

Head and Neck.

Occipito-frontalis. moves scalp and raises eye brow.
Orbicularis palpebrarum. shuts the eyes.
Levator palpebrarum. opens the eyes.
Temporal. raise the lower jaw.
Masseter. " " " "
Sterno-cleido-mastoid. depresses head upon neck and neck upon chest.
Platysma myoides. depresses lower jaw and lower lip.

Trunk.

Pectoralis major. draws arm across front of chest.
Pectoralis minor. depresses point of shoulder,
Latissimus dorsi. draws arm downwards and backwards.
Serratus magnus. assists in raising ribs.
Trapezius. Rhomboideus. backward movements of head and shoulder,
Intercostals. raise and depress the ribs.