14.  The three rows of projections called the “knuckles” are formed by the proximal bones of the several joints.  Thus the first row is formed by the ends of the metacarpals, the second by the ends of the first phalanges, and the third by the ends of the second phalanges.  That is, in all cases the line of the joints is a little in advance of the knuckles and nearer the ends of the fingers.

II.  Muscular Landmarks.

1.  The position of the sterno-mastoid muscle as an important and interesting landmark of the neck has already been described (p. 70).

2.  If the left arm be raised to a vertical position and dropped to a horizontal, somewhat vigorously, the tapering ends of the pectoralis major and the tendons of the biceps and deltoid may be felt by pressing the parts in the axilla between the fingers and thumb of the right hand.

3.  The appearance of the biceps as a landmark of the arm has already been described (p. 70).  The action of its antagonist, the triceps, may be studied in the same manner.

4.  The sartorius is one of the fleshy landmarks of the thigh, as the biceps is of the arm, and the sterno-cleido-mastoid of the neck.  Its direction and borders may be easily traced by raising the leg,—­a movement which puts the muscle in action.

5.  If the model be directed to stand on tiptoe, both of the large muscles of the calf, the gastrocnemius and soleus, can be distinguished.

6.  Direct the model, while sitting upright, to cross one leg over the other, using his utmost strength.  The great muscles of the inner thigh are fully contracted.  Note the force required to pull the legs to the ordinary position.

7.  With the model lying in a horizontal position with both legs firmly held together, note the force required to pull the feet apart while the great muscles of the thigh are fully contracted.

8.  In forcible and resisted flexion of the wrist two tendons come up in relief.  On the outer side of one we feel the pulse at the wrist, the radial artery here lying close to the radius.

9.  On the outer side of the wrist we can distinctly see and feel when in action, the three extensor tendons of the thumbs.  Between two of them is a deep depression at the base of the thumb, which the French call the “anatomical tobacco box.”

10.  The relative position of the several extensor tendons on the back of the wrist and fingers as they play in their grooves over the back of the radius and ulna can be distinctly traced when the several muscles are put in action.

11.  There are several strong tendons to be seen and felt about the ankle.  Behind is the tendo Achillis.  It forms a high relief with a shallow depression on each side of it.  Behind both the inner and outer ankle several tendons can be felt.  Over the front of the ankle, when the muscles are in action, we can see and feel several tendons.  They start up like cords when the action is resisted.  They are kept in their proper relative position by strong pulleys formed by the annular ligament.  Most of these tendons can be best seen by stand a model on one foot, i.e. in unstable equilibrium.