Determination of the Nature of the Hair
In examinations of this character use is made of the microscope. The hair to be examined is suspended in syrup, oil, or glycerine and placed between two thin glass plates. Human hair is sometimes cylindrical; sometimes flattened. It consists either of a central canal, or of a longitudinal series of oblong cavities which contain oily coloring matter, and possesses the same diameter throughout its entire length. The brown hair of the beard and whiskers, medium-sized chestnut hair, the hair of a young blonde girl, and the downy hair of a young man possess respectively a diameter of 0.03 to 0.15; 0.08 to 0.09; 0.06; and 0.015 to 0.022 millimetres. These exhibit on the surface slightly projecting scales, which are irregularly sinuous at the border, separated from each other by a space of about 0.01 m.m., and are transparent, whatever may be their color.
The hair of ruminants is short and stiff, and is characterized by containing cavities filled with air. Wool, however, forms an exception, as it consists of entire hairs, homogeneous in appearance and possessing imbricated scales, which bestow upon it the property of being felted.
The hair of the horse, ox and cow never exceeds 12 m.m. in length, and is tapering, its diameter gradually diminishing from the base. It is perfectly opaque, and does not appear to possess a central canal; has a reddish color, and frequently exhibits lateral swellings, from which small filaments occasionally become detached, in the same manner as a twig separates itself from the parent branch.