Towards the middle the hair becomes very narrow, but expands again and reaches its greatest diameter a little before the point.
Sheep’s wool is characterised by its surface structure of scales, the arrangement of which differs in the wool from different breeds of sheep. In some of the fibres the medullary canal is very manifest. Typical fibres of sheep’s wool are shown in the figures.
It is often necessary to distinguish between fabrics of cotton, linen, silk and wool, and in such cases the microscopical appearance of the fibres is invaluable as a preliminary test. Cotton is characterised by its curious corkscrew-like twists, and linen by its jointed structure, while silk has a long smooth cylindrical fibre, devoid of scales and showing little sign of structural formation.
In criminal cases neither cotton nor silk are likely to be claimed as human hair, although one may easily conceive the possibility of occasions arising where the composition of a peculiar material was a point of the utmost importance.
COTTON FIBRES
FLAX FIBRES
By kind permission of Messrs. Scott Greenwood & Co.