THE INTEGUMENTS AND CLOTHING OF MAMMALIA. 159 



inferior surface ; and the external laminae are the largest. In every essen- 

 tial, except in mere form, the hoofs resemble nails, or claws. The horn 

 of Mammalia, that is, the horny sheath investing the osseous core, in the 

 Ox and the Antelope, consists of hairs agglutinated into a mass ; in 

 many species, and especially in the Prong-buck 

 (Antelope palmata), the peculiar composition of the 

 horn is very apparent (fig. 172, the dotted line of 

 which shews its osseous core) ; generally, indeed, 

 the basal part (affixed to the cutis), and from which 

 its growth proceeds, shews the fibrous nature of its 

 structure. It is not necessary, however, that horn 

 should sheath an osseous core : in the Rhinoceros, 

 the horn of the nose is solid ; but, in structure, it 

 agrees with the sheath of the bony processes on 

 the head of the Ox. Baleen (or whalebone, as it is 

 commonly, though erroneously, called), which forms 

 pendent plates, lining the palate of the Whale, is of 

 Horn of the Prong-buck, the same nature, and consists of fibres, resembling 

 hair, agglutinated together, and very easily separable 

 from each other. Few Mammalia have spurs ; they exist, however, in 

 the tarsus of the male Ornithorhynchus ; they are essentially nails, or 

 horn, of a conical shape, sheathing a bone, or osseous support ; the spur 

 of the Fowl, and the beak of birds, also, afford examples of the horny 

 sheathing of bone. 



The chemical composition of hair, scales, and horn is the same ; the 

 essential appears to be gelatine and coagulated albumen. Vauquelin 

 detected two kinds of oil in hair ; one, varying according to the colour 

 of the hair from which it was extracted, black hair yielding black oil ; 

 the other, always white. Iron, oxyde of manganese, phosphate and 

 carbonate of lime, silica, and sulphur, have also been detected in hair. 

 Hair, submitted to the action of heat, in an open vessel, first swells, then 

 fuses, or liquefies ; subsequently, it emits a white flame, and resolves 

 into a black carbon. On distillation, it yields a reddish liquor, contain- 

 ing, prussiate of ammonia, a salt of ammonia, and an animal acid, which 

 Berthollet has denominated zoonate of ammonia. 



It is not within our limits to enter into the structure and growth of 

 feathers, the peculiar clothing of birds : it may be observed, however, that 

 they are nearly related to hairs, and are formed in a sheath, which, when 

 the feather is complete, falls off, in the form of scales, or scurf; the quill, 

 or barrel, is the last part finished, which done, the pulp of blood-vessels, 

 &c., dries up, leaving only that tubular, chambered membrane behind, 

 which is familiarly known, as it appears in the common goose-quill. 

 Feathers, perhaps, might be characterized as hairs, or spines, at a 



