and wounded a woodpecker and decided that choking was a 

 quick and painless method of killing the bird. After a long 

 effort the bird still appeared to be as much alive as at first, 

 which might indicate that there was some breathing source 

 other than the throat. The third division of the respiratory- 

 system is made up of a series of tubes leading from the 

 lungs, spreading out in all directions into a minute network 

 beneath the skin. Authorities agree on the various reasons 

 for this extensive breathing system, notwithstanding that 

 there are exceptions in nearly every instance. 



A bird is a quick breathing, hot blooded creature, (tem- 

 perature 106.9), consumes large quantities of food and is so 

 active as to be almost constantly in motion. These charac- 

 teristics are consistent with enormous quantities of energy, 

 which also require a corresponding amount of air for com- 

 bustion. 



One is able to hold the arm at a horizontal position for a 

 comparatively short time because the enormous demand 

 for energy to perform the task far exceeds tho supply. 

 To enable a bird to maintain itself on out stretched wings for 

 many hours, the wing must be rapidly supplied with energy, 

 hence the arrangement for large quantities of air to these 

 parts, as above mentioned. In short, the available storage 

 space is so inadequate that each wing might be said to main- 

 tain its own auxiliary plant to manufacture energy as re- 

 quired. Again, by this complete aeration of the body, its 

 buoyancy is increased. The ability to take a long breath is 

 undoubtedly appreciated by the song bird. Incubation re- 

 quires a constant quantity of heat, which is readily available 

 beneath the skin surface. The ability to fly is the great dis- 

 tinguishing feature between birds and mammals, the me- 

 chanics of which is a marvel of simplicity and perfection. 

 Omitting details we might say that the wing of a bird closely 

 resembles the human arm, although the movement at the 

 wrist is restricted to a plain hinged joint, just as if in the 

 human we were able to bend the hand to one side until the 

 little finger lay against the forearm. It is obvious that if any 

 rotary motion at this point were possible, wobbly and un- 

 stable conditions would exist in the wing so as to make it 

 well nigh impossible for the bird to fly. 



The muscular control and operation of the wing is most 

 interesting. In flying a bird makes its greatest effort, hence 

 the heavily meated breast. Also as this is the heaviest part of 

 the bird it is placed underneath, acting as keel and balance 

 while flying. Practically the entire wing operations are 

 controlled by these breast muscles, even the upward move- 



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