618 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Examples of each category are shown in Figs. 6 through 9. Also, a dramatic pair of before and after micrographs from an actual panelist, showing the im- provement after treatment, is shown in Figs. 10 and 11. To evaluate the degree of improvement resulting from the product treat- ment a numerical system was required. The difference ratio (DR), which is an index to measure the improvement of each damaged site, was devised and found to be a meaningful system to communicate the repair without being misleading. Each "before" and "after" pair of micrographs was classified into one of the four mentioned damage types, and each damage site assigned a danaage point from 0 to 4. (The higher the nulnber the more severe the damage.) The DR for ('ach site may be calculated by: DR = damage points after treatment damage points before treatment A value of 1.0 indicates no change with treatment. DR values below 1.0 shoxv improvement of a danaage site and those above 1.0 indicate additional danaage resulting from the treatment. A summary of the results is listed in Table II. Figure 7. Damage category-exposed cortex

SCANNING ELECTRON MICROSCOPIC TECHNIQUES 619 Figure 8. Damage category--split end Figure 9. Damage category-general shaft damage