Bookbinding and the Conservation of Books
A Dictionary of Descriptive Terminology

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hair

The coalesced horny cells, which contain the protein keratin along with 0.75 to 2.0% mineral salts. Although hair is an epidermal structure, it is seated deep in the papillary layer of the dermis. It consists of two continuous regions, the root and a long projection. which is the shaft. The lower part of the shaft is enclosed in a follicle which is a sheath of epidermal cells continuous with those in other parts of the epidermis. Most animal hairs are of two types: primary and secondary. Primary hairs are the more numerous and vary in structure depending on the age and species of the animal. Secondary hairs. which are similar in structure to the primary, are only about one-third their diameter.

The positions which the primary and secondary hairs occupy relative to each other as they enter the surface of the skin, together with their different thicknesses, determine the characteristic grain pattern of the dermal surface after the hair and other epidermis have been removed. Due to the general complexity of the papillary region, including hairs of various diameters at different stages of growth and located at different depths in the papillary layer, their removal by mechanical means is difficult. See also: HAIR-ON LEATHER ; HAIR SHEEP ; SHORT HAIR ; UNHAIRING . (248 , 291 , 363 )




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