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Per RIS 
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INTRODUCTORY CHAPTER. 
Brrps are the spoilt children of Nature—the favourites of creation. 
Their plumage often assumes the most resplendent colours. They 
have the happy privilege of moving in space—now fluttering through 
the air, hunting the insect which flits from flower to flower ; or 
soaring high aloft, to swoop upon the victim marked for its prey ; 
again cleaving the atmosphere, and performing journeys of vast 
extent with great rapidity. Mankind cannot fail to admire these 
winged beings, which charm at once by the elegance of their form, 
the melody of their song, and the graceful impetuosity of their 
movements. 
Anatomically speaking Birds, by their internal structure, are 
connected with the Mammifera, as their skeletons are nearly 
the same, only modified slightly for the purpose of flight. How- 
ever, in them there is a double circulation. The heart consists 
of two moteties, or lobes, known as the auricle and ventricle. 
It is conical in form, and occupies the anterior part of the thorax, 
its apex passing betweer. the lobes of the liver; but there is little 
perceptible distinction between auricles and ventricles. Their 
blood is richer in globules than that of the Mammalia, being more 
thoroughly permeated by air ; the respiratory function is also more 
energetic, from the same cause—in fact, they consume a larger 
quantity of oxygen, and produce a proportionately greater degree 
of heat; for while their lungs are small, and placed in the upper 
part of the thorax only, where they are confined on each side to a 
cavity, bounded above by the ribs, and below by an imperfect 
diaphragm, they are perforated by tubes, which communicate 
with membranous cells, distributed over the thoracic and abdo- 
minal cavities, between the muscles, and beneath the skin—often 
