HAIR AND WOOL in Merino wool fibers, the two portions lie side by side, each comprising about half the cortex, and are wound around each other in phase with the fiber crimp (10, 11) in crimpless wools, the ortho component occupies the core of the fiber, and the para is located around it in the form of an annulus (12). No such differentiation is noted in Caucasian hair fibers their cortex appears homogeneous, and it resembles the para component of the wool fiber cortex in composition and properties (113). The protein within the cortical cells is organized in the form of paral- lel micro fibrils, embedded in a matrix. The microfibrils, which repre- sent the crystalline component of the structure, contain little or no sul- i i i i WooI-Speakman, 1929 Hair-ChamberlainAWOOL1931Speakman,and I I i I 20 40 60 80 RELATIVE HUMIDITY, % 100 Figure 1. The adsorption regain isotherms of wool (19) and hair (20) fur the matrix is sulfur-rich and amorphous (14). In the para-portion of the fine wool cortex and in the cortex of hair, the micro fibrils are packed in a hexagonal array. In the ortho-cortex of wool or mohair, the micro fibrils are arranged in the form of whorls or spirals the con- trast between the microfibrils and the matrix, as revealed by staining with osmium, is much lower (14). The innermost morphological component, the medulla, is not invari- ably present either in wool or in hair, though it is more common in hair. In any case, it is believed to make little or no contribution to the chemi- cal and mechanical properties of the fiber. 2. Chemical Composztion A keratin fiber does not constitute a single chemical entity. As al- ready indicated, a complex substructure is present even within the individual morphological components. Thus, the whole fiber is clearly

772 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS COTSWOLD WOOL ,,••n and Stott] 0 I I • -' 0 1 2 3 l pH Figure 2. The swelling of wool (21) and hair (23) in aqueous HC1 a mixture of proteins, and a total analysis represents an average value. The cuticle contains more cystine than the cortex (15), and there are differences in other amino acids, also (16) the para-cortex of wool con- tains more sulfur than the ortho-cortex (13). It is therefore to be ex- pected that hair, with a higher ratio of cuticle to cortex and a cortex which is wholly para in nature, should differ significantly in its amino Table I Tensile Properties of Merino Wool and Hair at 21øC Property At 65% R.H. (24) In pH7 Buffer (25) Hair Wool Hair Wool Initial modulus, mg cm -2 Stress at yield point, mg cm -2 Stress at 20% extn., mg cm -2 Extension to post-yield, % Post-yield modulus, mg cm -'2 Extension at break, % Stress at break, mg cm -2 55 1.16 . . . . . . ß . . 37 2.0 31 0.62 ß . . 2O 1 1 21 12 0.52 0.45 27 29 5.3 3.4 51 41 1.7 0.8 Table II Dye Uptake of Different Fibers (7) Diffusion Coefficient Fiber Half-Dyeing Time (Hr) (Arbitrary Units) Human hair A 56 7.5 Human hair B 44 7.8 Human hair M 47 8.5 Human hair N 54 8.7 80's Merino wool 1.8 10.7 56's Down wool 2.0 17.4