Book II. ANIMAL ANATOMY, 283 



the asperities become less sensible. "When the wool is made into cloth, it is necessary to remove the oil, 

 which is done by the process of fulling. The cloth is placed in a trough, with water and clay, and agitated 

 for some time. The oil is removed by the clay and water, while the agitation, acting like pressure, brings the 

 hairs into closer union, and the cloth is taken out, not only cleansed, but felted. The hairs of every thread 

 entwine themselves with those which are contiguous ; so that the cloth may be cut without being sub- 

 ject to ravel. It is to this tendency to felt that woollen cloth and stockings increase in density, and con- 

 tract in dimensions, by being washed. In many places woollen stuffs are felted, on a small scale, by 

 placing them in running water, or under cascades ; and the Zetlanders expose them to the motions of 

 the tides, in narrow inlets of the sea. 



1817. In general there is a close connection between the color of the hair and that of the mucus web. 

 This is displayed in those animals which are spotted, in which the color of the skin is generally variegated 

 like that of the hair. 



1818. Hairs differ remarkably inform. In general they are round. Frequently 

 on the body they are thickest in the middle. Sometimes they are flat, or two-edged ; 

 and, in the whiskers of seals, they are waved on the margins. In many animals they 

 are long and straight ; while, in others, they are crisped, and are then termed wool. 

 When stiff', they are termed bristles; and, when inflexible, sjnnes. 



1819. Hair grows by the roots. In some species they are renewed annually; and in 

 all they are readily reproduced. 



1 820. Hair is the most permanent of all the substances consisting of animal matter, 

 resistmg putrefaction for a great length of time. 



1821. i^^aMers are nearly related to hairs; they consist of the quill, shaft, and web. 

 The quill, like the hair, takes its rise in the cellular membrane : the central portion of 

 the shaft has a texture like cork, and the web which usually occupies both sides of it is 

 composed of what are called barbes, and the sides of these with barbules. Feathers 

 exhibit great difference as to color : in some birds it varies with the seasons, in others 

 with food, and in others with the extinction of life. Like hairs, feathers are not only 

 renewed periodically, but they are readily reproduced, if accidentally destroyed. 



1822. Horns take their rise in the same situation as hairs or feathers. They may be 

 regarded as hairs agglutinated, and forming a hollow cone. The fibrous structure of 

 horn may be perceived in many animals at the base, where it unites with the skin. At 

 this part it receives the additions to its growth, the apex of the cone being pushed out in 

 proportion as the increase takes place at the root, and on the inner surface. But horns 

 differ remarkably from hair, in having their central cavity filled by a projection of bone 

 or other solid substance from the body beneath. 



1823. The different markings of the horns, particularly the transverse ridges, are indications of thedif- 

 ferent layers of growth ; and in many cases the number of these ridges corresponds with the years of 

 life. 



1824. The color of the horn is, in general, distributed through the mass ; sometimes, however, it is col- 

 lected into bands or threads. It seldom experiences much change during the life of the animal. It is 



Eermanent, or does not experience those periodical renovations which we have stated to take place with 

 air and feathers. The deciduous horns of the stag are different in their nature from true horns, and 

 will be afterwards taken notice of. The term horn is usually restricted to the coverings of the projections 

 of the frontal bones of oxen, sheep, and similar quadrupeds ; but various appendices of the skin, composed 

 of the same materials, and equally permanent, although seated on other parts of the body, may with 

 propriety be included under the same appellation; among these may be enumerated beaks, hoofs, claws, 

 nails, and spurs. 



1825. Beaks. The substance of these covers the external surface of the maxillary 

 bones of birds, and is ccJmposed of horn. 



1826. Hoofs resemble horns in their manner of growth, and in containing a central 

 support, formed by the termination of the extreme bones of the feet. They grow from 

 the inner surface and base, and are thus fitted to supply the place of those parts which 

 are worn away by being exposed to friction against hard bodies. Hoofs are peculiar to 

 certain herbivorous quadrupeds. 



1827. Claws resemble hoofs in structure and situation, deriving their origin from the 

 skin, having a bony centre, and occurring at the extremities of the fingers and toes. 



1828. iVai/s differ from horns and claws, in the circumstance of not being tubular, 

 but consisting of a plate generally convex on the outer surface, and concave beneath. 



1829. Spurs occur chiefly on what is termed the leg (tarsus) of gallinaceous birds. 

 They are found, likewise, on the ornithorynchus. Like horns, they are supported in 

 the centre by bone. 



1830. Harris, hoofs, and sitnilar parts, bear a close resemblance to one another in che- 

 mical composition. When heated they soften, and may be easily bent or squeezed into 

 particular shapes. They consist of coagulated albumen, with a little gelatine ; and, 

 when incinerated, yield a little phosphate of lime. 



1831. Their use, in animal economy, is to protect the soft parts from being injiirod by pressure against 

 hard bodies. They are in general wanting, where the parts are in no danger of suffering bom the in- 

 fluence of such agents. When torn off from the base, they are seldom completely renewed, although 

 very remarkable exertions are frequently made by the system to repair the loss. 



1832. Scales vary remarkably in their form, structure, mode of adhesion, and situation 

 in different animals. In general they are flat plates, variously marked. In some cases 

 each scale consists of several plates, the lowest of which are largest ; so that the upper 

 surface becomes, somewhat imbricated. Some scales adhere by tlie whole of their cen- 

 tral surface ; while others resemble the human nail, in having the distal extremity free. 



