334 CZl CZl aJ JOURNAL OF COSMETIC SCIENCE Figure 7. Extended hair surface. a: Asian hair. b: Caucasian hair. 1.20 □ before extension Ill after extension 1.15 1.10 1.00 Asian Caucasian Figure 8. Roughness of the cuticular outline. On the whole, in the case of Asian hair, collapse around cuticular edges and delamination was hardly observed. However, in contrast, such damage was seen in over half of the Caucasian samples. In sections nearer to the hair tip, where aging is expected to have proceeded further, both types of hair were damaged more severely and similarly. PARTICULATES OBTAINED FROM EXTENDED AND SONICATED HAIR Figures 9a and 96 show the typical particulates collected by filtration from extended and sonicated hairs. In the case of Asian hair (Figure 9a), the outlines of the substances look smooth and their surfaces appear flat. From their appearance, it can be assumed that this is the outer side of the cuticle cells (A-layer side). On the other hand, in the case of Caucasian hair (Figure 96), both the outline and surface appear rough and the substances are relatively small, compared with those from Asian hairs. From their roughness, these materials cannot be considered to originate from the outer side of the cuticle cells.

MORPHOLOGY OF ASIAN AND CAUCASIAN HAIR 335 Table II Classification of damage Sample name Roughness Deposits Delamination Asian Al A2 A3 A4 AS A6 + + A7 A8 A9 Caucasian Cl C2 + + C3 + C4 +* cs + + + C6 +* + + C7 + cs + + * Only slight difference found. Figure 9. Particulates obtained from extended and sonicated hair. a: From Asian hair. b: From Caucasian hair. Therefore, we can assume that they come from the inner side of the cuticle cells and are probably endocuticle. The deposits found at the cuticular edges of extended hair may also be considered to be a part of these substances. MEASUREMENT OF CUTICULAR ELASTICITY Figure 10 shows the results of nanoindentation measurements of cuticle cross sections. It was shown that the endocuticle of Asian hair was harder than that of Caucasian hair. The exocuticle of Asian hair was similar to or only slightly harder than that of Caucasian hair. The difference in elasticity between exocuticle and endocuticle was larger for Caucasian hair than for Asian hair, as indicated by the ratios of exo/endo (for Asian hair: 1.26 for Caucasian hair: 1.41). This means that the hardness of a whole Caucasian cuticle cell is relatively uneven. From these results, it was found that there is a difference, not