COMPARISON OF BEARD AND SCALP HAIR 379 Table VI Amino Acid Contents of Caucasian Scalp Hair and Beard Hair (micromoles/g) Type of Amino Acid Scalp Hair a Beard Hair b Cysteic Acid 30 19 Aspartic Acid 431 463 Threonine 539 484 Serine 1,121 971 Glutamic Acid 997 964 Proline 615 634 Glycine 448 452 Alanine 345 354 Half Cystine 1,170 963 Valine 363 322 Methionine 31 30 Isoleucine 152 162 Leucine 456 468 Tyrosine 112 128 Phenylalanine 90 98 Lysine 247 285 Histidine 56 60 NH 3 797 777 Arginine 586 552 •Bulk hair from De Meo Brothers. bBulk hair from ten subjects. Duplicate evaluations, variations about + 10%. 25 • 20 ß ß Sc•lp i I i i i 100 150 200 250 300 Time (minutes) Figure 16. Rate of solubilization of Caucasian scalp and beard hair in urea-bisulfite solution. Triplicate analysis on bulk hair.

380 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS relative number of randomly distributed disulfide bonds in the fiber. This technique was used to determine the comparative swelling rates of beard and scalp hair. In 97% formic acid the volume swelling (Vi•) of Caucasian beard and scalp hair was determined to be 0.41 + 0.02 and 0.44 _+ 0.02, respectively. Since Vi• was defined as the volume of dry hair expressed as a fraction of the volume of swollen hair, the lower volume swelling index for beard hair indicates a higher degree of swelling and thus a lower degree of disulfide bonding. In good agreement with the above studies, Caucasian beard fibers exhibited a faster rate as well as a higher degree of swelling in 97% formic acid, than scalp hair of similar diameter (Figure 17). 7O ojø .m E .e_ 20 10 I I I I i I 2 3 4 5 Time (minutes) Figure 17. Diametral swelling of Caucasian beard and scalp hair in 97% formic acid solution. Each data point is the average of measurements from five fibers for each of five subjects (25 samples). d. Permanent Set and Supercontraction Supercontraction and set are characteristics of keratin fibers in certain media (22), and their level is principally dependent on the chemical composition of the cortical regions of the fibers (23). As fiber thickness is another parameter influencing the level of set incurred (23), facial and scalp hairs of similar diameters were selected for this study.