Muscles and Nerves 1g1 
we shall see a tangle of bundles of red flesh—the muscles 
which unite to make the arm of a bird such an exquisite 
flying-machine. Where a muscle narrows and is fastened 
to a bone, its fibres merge into a thin, tough white cord— 
Fic. 140.—Model of bird’s foot, showing perching tendons; toes extended. 
a tendon. This is not elastic like the main portion of 
the muscle, but is much more tough. 
In the slender legs and feet of birds there is little more 
than bone, tendon, and skin. The tendons which clasp 
and unclasp the toes are very interesting, and if we will 
