208 THE STRUCTURE AND LIFE OF BIRDS cnHap. 
Great Depressor and the Elevator from the bone while 
leaving their tendons attached to the’ humerus, 
then pull them and watch the result. Much that 
otherwise must be obscure then becomes perfectly 
clear. Not the least interesting point is the way in 
which the Elevator, being attached. where it is, raises 
the front or prasaxial margin of the wing, so that in 
attaining its position for a fresh stroke it turns the 
edge to the air arid meets with little resistance. These 
two muscles can also be worked at the same timie, the 
one antagonising the other; the Depressor lowering 
the wing to the horizontal, while the Elevator holds 
the przaxial margin fast, so that the hinder part 
cannot be tilted up. A bird sets his wings thus when 
he wishes to halt. A movement that looks perfectly 
simple may be due to the combined action of a 
number of muscles. 
The Spreading of the Wing. 
It is a strange thing that in these days when it is 
boasted that machines can be made to do most things 
that a man can do, that sailors should still have to 
run up the rigging, be the weather foul or fair, and 
straddle across the yards in order to furl or set 
the sails. It would not seem to be beyond human 
ingenuity to devise machinery by the aid of which 
this work should be managed from the deck. Some 
progress towards this has, I believe, been made. In 
the bird we find such machinery brought to great 
perfection. Instead of men we have muscles, and by 
the machinery of tendons and ligaments these muscles, 
