The top bone is the os calcis, or hock bone, to which the tendon Achilles is attached.
On the anterior or extensor surface of the limb a powerful tendon (7 in fig.
9, Tendon of deep flexor (fl.
In the hind-leg, the perforated tendon is a continuation of that of the plantaris, passing pulley-wise over the tuberosity of the calcaneum.
We have here the interesting fact that a muscle (portion of the triceps humeri of the reptiles) has been reduced to a tendon, which in a secondary way has become connected with cutaneous muscles, which, when strongly developed, represent its belly.