FEMALE SCALP 221 FIBER COLLECTION FOR DIAMETER DETERMINATION Small areas, in the general location where fiber counting had been carried out, were randomly preselected. All fibers within this area were cut off at the skin line. About 30 fibers were collected from each individual. Compound and group 6bets were marked and kept separately from others to allow evaluation of intragroup and intracompound variations. The collected 6bets were cleaned with an ether rinse, and dried at room temperature. All further treatment and measurements were carried out at 70øF and 65 per cent RH. The fibers were individually cut to an exact length of 5.00 cm in a straightened configuration with the aid of a special instrument (19). The 5.00 cm length was cut starting about 1 cm from the original skin line of the fiber and, therefore, en- compassed the last 4 to 6 months of growth. The 5 cm long fiber segments were indi- vidually weighed on an electrobalance to the nearest 0.1 /xg. The idealized average cylindrical diameter was calculated from the weight of each fiber according to the following: D = 20 X/W/(3.14 x 1 x d) where D equals diameter in micrometers W equals weight in micrograms I equals length in centimeters = 5 and d equals density of fiber in g/cm a = 1.3. Correlations among different measured values were calculated according to a standard statistical program package supplied to our computer. RESULTS AND DISCUSSION HAIR COUNT A large proportion of the scalp fibers grow in groups. The fibers within a group are closely spaced, but the distance between neighboring groups is considerable, about 1 min. In order to minimize errors originating from the significant intergroup distance, the fibers were counted over a relatively large area--1 cmL This was in contrast to some earlier work (10, 11, 12, 13, 14, 15, 16), where the fiber number was determined in 2 mm squares. The results are shown in Table I. The age of the subjects ranged from 24 to 59, but only 3 participants were over 42. Since both age and racial origin have been reported to influence some of the measured characteristics (10, 11, 13, 16, 20, 21, 22), the average values are given both with and without the inclusion of the Chinese panelists. On the basis of the present work, it can- not be determined whether the differences seen between the 2 averages were due to racial or age factors. The number of fibers/cm 2 ranges from 95 to 295 with a mean of 211. Subject number 1--with the extremely low fiber count--shows signs of diffuse allopecia, associated with age, which was confirmed by photographs of her going back a few decades. The next 4 individuals with fiber counts under 160 fibers/cm 2 include 2 over 45 years of age (Chinese) and one of Spanish origin (number 4) with very dark hair. Number 3 has light brown hair and, according to her account, never had had more hair. The remainder of the panel had more than 190 fibers/cm 2. The correlation between decreasing hair count with increasing age is rather weak 0.601. This does not negate earlier findings that both hair and follicle numbers decrease with age (13, 16, 22). Our study did not include extreme ages, and even within the range, 85 per cent of

222 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Table I Fiber and Site Count on Left Side of Head Number of Fibers/ Number of Sites/ Average Number of Fibers/ Subject Age cm 2 cm 2 Site 1 59 a 95 48 2.0 2 48 a 131 58 2.3 3 29 145 67 2.2 4 37 153 86 18 5 47 • 159 64 2.5 6 30 195 72 2.7 7 36 196 84 2.3 8 36 205 76 2.7 9 27 206 88 2.3 10 42 208 105 2,0 11 24 227 87 2.6 12 26 231 88 2.6 13 33 233 82 2,8 14 42 243 110 2.2 15 31 245 98 2.5 16 31 250 110 2.3 17 31 251 108 2.3 18 36 275 101 2.7 19 37 279 98 2.8 20 28 295 90 3.3 Average b 35.5 211 86 2.4 Average c 32.7 226 91 2,5 •These subjects were Chinese, all others apparently Caucasians. bAyerage for the 20 subjects. CAverage for the 17 Caucasian subjects. the participants were between 24 and 42. If the 3 oldest individuals are left out, the correlation between age and hair count approaches zero, indicating that this age group is rather homogeneous, or at least the individual variability--probably due to inherited factors-•is a stronger parameter than age for this sample size. The values of the average fiber count/cm'--211 and 226---are noteworthy in the respect that they are practically identical with those given by Barman (10, 11, 13, 15, 16), although, different from some others cited by Giacometti (22). A full head of adult hair is commonly stated to contain about 100,000 (3, 5) to about 120,000 (4) fibers. According to Behrman (23), the average scalp area for an adult is in the range of 775 cm =. Using this figure, the fiber density would only be 129 fibers/cm = for a 100,000 fiber adult head of hair. Only 1 individual in our panel was below this number. With the presently obtained fiber densities of 211 and 226 fibers/cm •, the full head of hair should comprise 164,000 and 175,000 fibers, respectively. Although the densities were determined only at a specific site on all heads, this site is neither an outstandingly dense hair growth area nor are the d'ifferences among different scalp areas very large on adult heads (13, 14, 15). Therefore, we believe the estimate for the average fiber content of a full head of hair should be raised to the 160,000 to 180,000 range for women in the age group of 25 to 50. The commonly used low figures probably originate from the works of Stelwagon and Pinkus (24) quoted and even misquoted later (25, 26).