20 INTRODUCTION. 



Their lungs are small, and incapable of much dilatation, but 

 they communicate by apertures, with cells or membranous 

 sacs situated in the chest, and among the muscles, and be- 

 tween them and the skin, and even with the cavities of the 

 bones. Hence their respiration is said to be double. They 

 have an internal skeleton, for the support and motion of the 

 parts ; are furnished with muscles, or organs subservient to 

 motion ; with three double organs of sense, namely, eyes, 

 ears, and nasal cavities ; with a tongue, which is partly 

 an organ of taste, partly of prehension, and with a general 

 sense of touch or feeling situated in the skin. Organs of 

 assimilation, for the conversion of external substances into 

 their own nature, and of propagation, for the continuance 

 of their species, are also to be enumerated ; together with 

 other parts, which require to be somewhat particularly ex- 

 plained. For this purpose, let us take any bird, in which 

 the external parts are easily distinguished, a Shrike, for 

 example. 



A bird may be divided into : the head, a ; the neck, 6 ; 

 the body, cc ; the tail, d ; the anterior extremities or wings, 

 ee ; and the posterior extremities, or legs and feet, ff. The 

 Head is composed of the brain, its membranes, the bones of 

 the skull and face, the organs of seeing, hearing, smelling, 

 and tasting, with those for the prehension and swallowing of 

 food, and various other subordinate parts. The Neck is the 

 more or less elongated and flexile part by which the head 

 is joined to the body, and is composed of the cervical ver- 

 tebrae, various muscles, the oesophagus or gullet, the wind- 

 pipe, nerves, and bloodvessels. The Body is the basis of 

 the whole, consisting of the dorsal and sacral vertebrae, the 

 ribs, the breast-bone, the clavicles, the heart, bronchi, lungs, 

 liver, stomach, intestines, kidneys, genital organs, and va- 

 rious other parts. The Tail is composed of the caudal or 

 coccygeal vertebrae, their muscles, and the tail-quills. The 

 Anterior Extremity consists of the bones of the scapula or 



