Observation methods
In this section
Observations of hair samples
Hairs were observed using two methods, by inspecting, measuring and photographing the hairs with 1) the naked eye and digital SLR camera (macro observations) or 2) using a polarising microscope (micro observations).
Macro observations: Hair type, length, profile and colour
Hairs were observed and photographed at macro scale to determine hair type, length, profile and colour. Photographs were taken using a digital SLR camera (Canon EOS 1300D fitted with a Canon EFS 60mm macro lens) mounted on a focus rail stand. Two methods were used for taking images. In the first method, hairs were placed on a white card adjacent to a ruler and weighted down with a microscope slide. The card was place under the camera, and photographs taken using an overhead desk lamp for illumination. In the second method, hairs were placed on a microscope slide, weighted down with a cover slip and placed on a purpose-built lightbox (trans-illuminator for macro photography) under the camera.
Micro observations: Hair diameter, scales, medulla and cross-sections
Hairs were observed and images (called micrographs) captured at a microscopic scale to determine hair diameter, scale patterns, medulla type and cross-section shape. Hairs were placed on a microscope slide and covered with a large rectangular cover slip. No additional mounting medium was used, to avoid changing the hairs in any way. Similarly, scale casts were not taken to avoid contaminating the hairs with casting media. Hairs were observed and photographed using a polarising microscope with digital camera and software attached (either a Leica DMRX polarising microscope with integrated DMC2900 camera and LAS software, or a Nikon Eclipse LV100N POL microscope with integrated Nikon DS-Ri2 camera and NIS-Elements software (Version 4.50.00)).
The microscope slide was placed on the rotating stage of the microscope for viewing. The full length of the hair was firstly viewed at low magnification (10x objective lens) to determine whether the root and tip were present. The diameter of the hair was then measured at the widest point observed along the hair (using 20x objective lens). This only represented the maximum diameter of the hair if both the root and/or tip were present. If they were absent, it is possible the widest part of the hair was also missing. Hairs from artefacts are often missing the root and/or tip. Hairs from some mammals may be missing the tip (e.g. humans have haircuts and sheep are shorn).
Scales on the hair were observed by manipulating the microscope focus to highlight the outer surface of the hair. Details of the scales were also enhanced for viewing by using both the transmitted and reflected light mode of the microscope. Observations were made at high magnification (20x and 40x objective lens). Scale descriptions made using this technique were compared with observations from scale casts prepared from a sample of hairs from a live dog. It was found that scales could be reliably described without preparing scale casts.
The medulla of the hair was observed using both plane polarised and cross-polarised light, at higher magnifications (20x and 40x objective lens). The appearance of the medulla under plane polarised light enabled comparison with published images. Cross-polarised light was used to further enhance the appearance of features within the medulla. The colour of the hair and presence of pigment granules in the cortex were checked using plane polarised light.
Although the cross-sectional shape of hairs is considered an important diagnostic feature, it requires a large enough number of hairs to give a good representation. The number of hairs available for analysis, particularly from artefacts can be limited. The preparation of cross-sections also damages the hair. The preparation of hair cross-sections for microscopy are described in Brunner and Coman (1974). This technique was used for some hair samples in this database.