TEGUMENTARY SYSTEM. 65 



CLASS II. AVES. BIRDS.* 



TEGUMENTARY SYSTEM. 



As the body of the Mammalia is very generally covered with hair 

 so that of Birds is clothed with feathers, which belong, like it to 

 the epidermic structures. The skin of the Mammalia is much 

 stronger than that of Birds, for although the larger Wading, Aquatic 

 Birds and the Ostriches, have a thick hide, yet the corium is 

 in general throughout the class thin, transparent, and very highly 

 vascular, from the large follicles of the feathers which penetrate 

 into the subcutaneous cellular tissue being supplied by numer- 

 ous vessels. The epidermis is exceedingly delicate upon those 

 parts of the body where feathers are met with, but dry and con- 

 stantly desquamating. In featherless parts, as upon the head and neck 

 of many Birds, it becomes very much thickened, and forms callosi- 

 ties, wattles, and combs, in which, in addition to the cellular, 

 what are called the erectile and elastic tissues are often devel- 

 oped, while at the same time red and blue pigmentary cells occur 

 beneath the epithelium. Beneath the integument are found, as in 

 Man, the subcutaneous mucous crypts, which are particularly con- 

 spicuous, as in Aquatic birds, upon the joints of the posterior ex- 

 tremities. Upon the toes and feet there occur plates and scales of 

 horny tissue, and both the toes and beak are invested by laminiform 

 horny sheaths, which may be completely detached from the bony 



* Class AVES. 

 Order I. Acci , RAPACES 



SEx. All true singing Birds and those which, having no song, 

 yet possess a complicated inferior larynx, as the Sparrow, 

 Rook, Shrike, $c. 



fEx. Woodpecker, Cuckoo, Parrot, Toucan, with those gen- 

 era which, though related by external characters to the 

 singing Birds, are devoid of a muscular vocal appara- 

 tus,, viz., Alcedo, Upupa, Merops, Cypselus, Trochilus, 8fC., 

 and constitute the subdivision Picariue. 



IV. GALLING. Ex. Pheasant, Turkey, Partridge, Pigeon. 

 V. BREVtPENNESorSTRUTHoKiD^. 71 ' Ouwuwy, Emeu, Ap- 



VI. GRAM .K. Ex. Bustard, Heron, Snipe, Flamingo. 

 VII. PALMIPEDES. Ex. Divers, Albatross. Pelican, Goose. 



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