142 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS "Figure 2.--Autoradiograph, corresponding to Fig. 1, of living guinea pig skin treated with C•2H25Sa•O4Na for sixty minutes. Radioactivity is shown in the first (external epidermal section, lower right corner) to the thirty-second tissue section. of the radioactivity in the tissue sections beneath the epidermis may be caused by the accumulation of tagged surfactant in the hair follicles and ducts. This observation is substantiated by Figs. 3 and 4. The magnified specimen area shown in Fig. 3 is the seventeenth section at a depth of 425 microns beneath the epidermal surface. It can be seen that the radio- activity found on the autoradiograph, Fig. 4, coincides with the location of hair follicles and sebaceous ducts in the tissue section. The autoradiographs from the nonliving skin specimens showed that the majority of the radioactive material was present superficially on the epidermis with small amounts found in the upper derreal layers. From the experiment with nonliving skins secured over the top of metal chambers containing distilled water., further evidence was obtained to indicate that little or no absorption of the tagged surface active agent occurred. None of the aliquots of water removed from the chamber after one-half to twenty- four hours contained radioactive material. It is important to note that the untreated control tissue produced a negative autoradiograph. The developed x-ray film incubated over the untreated sections showed no radioactivity after a period of four weeks.

AUTORADIOGRAPHIC STUDIES ON PERCUTANEOUS ABSORPTION 143 . ,•. -:. .. .. ,. •.- :,.•-• • , • . ._ ......... •'•' '-'•":•'.• '• .... '• •-'. •:-' ...•.:. • . •-.a • ".. • ..... • ..... : --- :... •i: :'•. . ... :. . .- • .:- •. - • •:• . • •-:.:• •..• -.•• . • .,.: .... • .... •.•.:•. ..•. t•..•.• :•.• '"• ••- •. ..• , • '• •-.-?- : '.•&... .•.•-- .• • .... .y -, ...q• :•--• ..- •w.. ß .. K • ? .• . . -:• - ,... • • - '•.•. •-•. •. .. ...• . . •::• ....... :.. •..• •- • '-L .'.. • '•. • • • .•-.:"' ..'.• ' ..' ...' 7 • •:' ' :•' ' '.' •'• ""•%'•5: •'•"... :.•: :'. -•' ' ¾ .... ff:•i?:' • •.• •:--:' :, -:-• .... •. •-' •- --:• •4 •-•'v "•':: -' •, - a •, '- ....... : ' 3--' • • • •'•: •" "'- -'- ' • '• .... ' Fibre &--Photograph of an area of the seventeenth tissue section repre- sented in Fig. 1. Magnification 200X. • ...... "& ...... :• -.:....:. • .... .... • .....4 ¾•... • .. • ..• • : •--::•e "•. • ,- ..•* --•.•:.... -"' '•: ' -'. ß - •' ß '• • •2. . '•5• •--:• m •..-':. ,•' .-•. - .. ' .. j• 4 ..- •: .--- • . ...• •.. •:.•..- . ..:•.•. --.-•- .•.•,.• .• , 5•%.•---:•. ... •,..•= ---• •. ----• -.• .•%_ -•:.• .. r-• - • (•:- ":•: -• ::--..•:.• --.. . •..:. ? .. :•:• -..- ...-- •:.: C.•$•. • :'v-- ', - .... . ..... .'.• Figure •.--Corresponding autoradiograph of the area of the sevent•nth dssue secuon represented in Fig. 3. Radioactivity is shown to be concen- •ated in the pilosebaceous apparatus. Magnification 200X.