INTERNAL STRUCTURE CHANGES OF EYELASH INDUCED BY EYE MAKEUP 221 (5). The resemblance between eyelash and scalp hair is in agreement with the previous re- ports that observed eyelashes using transmission electron microscopy (TEM) (4,6). The difference of internal structure between eyelash and scalp hair is not clear at present. As shown below, the shapes and sizes of eyelashes were varied with samples from different- people. We have observed scalp hair samples from only one person (5), and the structural characteristics of scalp hair were in the range of variations of eyelash samples. Using the reconstructed cross-sectional images, the sizes of specifi c regions of the eye- lashes were measured (Table III). In the reconstructed cross-sectional images, cross sec- tion of eyelashes had an elliptical shape, the mean length of the major axis was 77.8 μm, and the mean length of the minor axis was 63.2 μm. They are consistent with a previous study in which eyelash diameter was measured from digital photograms (4). By contrast, the mean thickness of the cuticle layers was 2.0 μm in this study, whereas it was measured to be 5.3 μm from TEM images in the previous study (4). In the TEM observation, the eyelash samples were pretreated by many steps of procedures containing fi xation steps using glutaraldehyde and osmium tetroxide. In this study, the eyelash samples did not undergo prior processing. The pretreatments prior to TEM imaging might have induced morphological changes in the cuticle. The relationships among these measurements were investigated (Table IV). The area of the fi ber correlated positively with the length of the major axis of the fi ber and the length of the minor axis of the fi ber. The ratio of minor axis of length versus major axis length did not correlate with area of fi ber. These correlations indicate that eyelashes of different sizes tend to have a similar shape. In contrast, the area of the fi ber correlated positively with the ratio of fi ber area versus medulla area. This means that the percentage of medulla space in total fi ber space tends to be wider in larger eyelashes. Similar correlation has been found in scalp hair (7). The thickness of the cuticle correlated positively with the major axis length, but not with the minor axis of the length. This characteristic seems to refl ect the negative correlation between the ellipticity of fi ber, the ratio of minor axis of length versus major axis length, and the thickness of cuticle. EFFECT OF EYE MAKEUP ON EYELASH STRUCTURE Cracks were observed in the cuticles of eyelashes (indicated by arrows in Figure 2), and the extent of the cracks varied among the samples. Factors underlying the formation of Table III Shape and Size of the Eyelashes Mean Standard deviation Length of the major axis of the fi ber (μm) 77.8 13.3 Length of the minor axis of the fi ber (μm) 63.9 10.5 Ratio of minor axis length vs. major axis length 0.826 0.073 Area of the fi ber (×100 μm2) 39.9 12.6 Area of the medulla (×10 μm2) 31.1 20.0 Ratio of fi ber area vs. medulla area 0.076 0.034 Thickness of the cuticle (μm) 2.05 0.64

Table IV Correlations between the Shape and Size Characteristics of the Eyelashes Length of the major axis of the fi ber Length of the minor axis of the fi ber Ratio of minor axis length vs. major axis length Area of the fi ber Area of the medulla Ratio of fi ber area vs. medulla area Thickness of the cuticle Length of the major axis of the fi ber 1 Length of the minor axis of the fi ber 0.860 (**) 1 Ratio of minor axis length vs. major axis length − (*) 0.184 1 Area of the fi ber 0.961 (**) 0.958 (**) −0.077 1 Area of the medulla 0.610 (**) 0.703 (**) 0.1 0.677 (**) 1 Ratio of fi ber area vs. medulla area 0.438 (*) 0.533 (**) 0.067 0.480 (**) 0.841 (**) 1 Thickness of the cuticle 0.459 (*) 0.25 −0.436 (**) 0.361 (*) 0.068 -0.088 1 Correlations were analyzed using Pearson’s method. Correlation coeffi cients are shown. * 0.05, **p 0.01. JOURNAL OF COSMETIC SCIENCE 222