94 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS , •- '"'•'•:':•?-r ............. •::•.•t,:•" •' '•'• ß .. '•-. . .:• . ...• .: •... .• .• ..:: ... • •:?• ..... .. .. . ." 7'.: "' !i ? '•i :.. ". ...... ....7-. i?'.i':i:,• ,:. ,:...' ...... '•' ...: '¾: "-?. ......... 'z .. •.• •'• Figure 12.--Cross section of hairs from dark-haired child. 500X magnification. •... ......: .7,.... • ß •.,'.: ... .. :.•,,, 37•:. ß ß Figure 13.--Cross section of red head hair of adult female. 500X magnification. Figure 17 shows a sample of the beard hair from the same individual. It is not only generally larger in cross-sectional area, but it is characterized by the presence of a triangular hair. This shape is not unusual in beard hair, but is rarely found in head hair. Cross sections of fibers are also useful where staining of fibers is to be

PHOTOMICROGRAPHIC TECHNIQUES FOR HAIR 95 .. .... ß ' ß ,•..,,,..c. :•,,,. .... "" ' -:"?' . .... ß ..... :.:.. -.•,, ':Y :'/' "" .....,•: .:•"•:' ' '•. ... ............ -:. Figure 14.--Cross section of child's head hair showing medullas. 500X magnification. :. .... .. Figure 15.--Cross section of female child's head hair which is almost perfectly circular. magnification. i 500X carried out. The principal applications for stains are in studying injuries to fibers, in identifying fibers and in studying the growth, biology and morphology of fibers. Keratinization, for example, has been studied extensively by histological methods.