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TYPES OF DOMESTIC SHEEP AND WILD LIFE [Vol. XXII, Part IV
and are either convexly curved or their free edges trace out a wave-shaped line
around the fiber shaft.
The reticulate or hair type of scale structure has the appearance of a rather
taunt net stretched across the surface of the fiber. The scales, although slightly
curved, appear rather straight and smooth-sided in comparison with those of the
wool type. More than two scales meet at a point, and they are often irregular in
size and shape.
Hausman [8], from his study of mammalian hair fibers, formulated his well-
known classification dividing the scale structure into coronal and imbricate forms.
The coronal scales completely encircle the corticle cylinder of the hair shaft, their
free ectal edges sculptured in various forms. The imbricate scales do not indivi-
dually encircle the corticle cylinder, but are arranged like the scales of a fish, with
their free distal edges etched into different shapes. The two groups of scales are
further classified according to their apparent structure. The coronal scales may be
simple, serrate, and dentate ; imbricate scales may be ovate, acuminate, elongate,
crenate, and flattened. Although the author did not include wool in his studies,
the crenate and flattened types are often encountered on wool fibers.
REVIEW OF LITERATURE
Although scale structure has not been studied extensively in the field of wool
technology, various workers have been interested in the examination of scale struc-
ture. Their methods may be classified under three main headings—direct examina-
tion of the fiber under the microscope ; half-mounting in media of refractive index
similar to that of the fibers ; and impression or cast methods in quick-drying media.
The direct examination of the fibers under the microscope was unfavourable
because of the non-availability of suitable mounting media, and the optical
difficulty in focussing wool due to its tridimensional character.
Half-mounting in media of refractive index similar to that of the fibers was
used to overcome some of the above-mentioned difficulties. By immersing the
fibers halfway in a mounting liquid, the lower part of the fibers becomes invisible
because of the liquid : only the fiber surface facing the observer is visible and can
be studied. Different media and techniques have been employed by Manby [14],
Reumuth and Schwerdiner [18], and Herzog [10], with satisfactory results.
The cast or impression method involves obtaining imprints of the surface
structure in a suitable quick-drying media, and then studying the imprints under
the microscope or by projection. Various media, such as resin, fingernail polish,
cellulose, gelatin, and thermoplastic film, have been suggested by different workers.
Saxinger [19], Herzog [9], Von Bergen and Mauersberger [21], Lockte [13], Hardy
[4], Hardy and Plitt [5], Koonz and Strandine [11], and Wildman [22] employed
different techniques to get cast impressions.
Earlier workers, such as Brevoort [2], McMurtrie [16], Hausman [6], and Manby
[14], used special staining techniques for the study of scale structure ; these methods
have lost popularity due to improvement of the impression method. Only a few
references are available regarding the specific scale patterns of different fibers.