EFFECTS OF GELATIN ON FINGERNAILS 447 thickness and can be avoided only by selection of the correct speed-weight- depth relationship. In our work the test nails, varying in length from 2--4 ram., were fastened to a steel block with cellophane tape with the long diagonal of the concave surface of the nail parallel to the axis of the indenter used to minimize erro• due to curvature. Three Knoop hardness determinations were made on each nail sample, and the average of the three determinations was recorded. The degree of hardness of the initial samples (Knoop Hardness Number) was recorded as the base line value, and all subsequent values obtained were compared on a relative basis to the initial values. An increase or gain in hardness relative to the initial readings was recorded as a positive (-3-) change and a decrease as negative (-). No change was recorded as zero (-0-) change. 300 250 200 • 15o O Gelatin 2,0 grams / d•y • Placebo 2.0 gramsIdly I00 - I Month 2 Months 5 Months Figure 1.--Average degree of hardness gain. The per cent change in hardness for each nail sample was calculated at each time interval specified. All data obtained were subjected to statistical evaluation using the chi-square method (7). In all instances the data were computed using a probability factor of 0.01. RESULTS The subjects in this investigation were studied through two seasonal periods. In the tabulation of the results, however, no particular variations due to seasonal effects were observed. The data obtained in these studies are given in Tables I and II. Tables III and IV and Fig. 1 set forth the results of the analyses of the data.

448 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS TABLE I--AvERAGE CHANGES IN HARDNESs--GELATIN REGIMEN Weight Load in Nail .-- Subject Grams Sample* Initial Knoop Hardness Numbers .... 1 Month 2 Months 5 Months B 4100 R-1 1,344 6,613 9,114 33,563 (Female) R-3 7,708 7,708 6,613 12,046 R-5 7,708 4,170 7,708 9,114 J L-4 3,211 6,810 8,698 14,491 (Male) 7100 R-4 3,211 8,158 10,650 17,253 R-5 1,752 5,781 6,810 4,310 K L-3 6,099 12,617 9,273 8,158 (Female) 7100 L-5 5,781 11,452 14,491 8,158 R-5 631 1,656 1,338 9,926 C 4100 L-5 11,452 5,355 5,732 6,613 (Female) R-4 3,338 10,918 9,967 7,708 R-5 5,773 40,340 48,216 6,612 I L-4 7,668 8,158 14,491 28,925 (Female) 7100 L-5 6,810 3,495 8,158 15,783 R-5 25,787 11,452 32,568 68,898 M L-1 414 526 502 572 (Male) 7100 L-3 509 654 666 772 R-1 3,946 6,099 8,158 9,926 N R-3 3,088 3,946 7,668 5,214 (Female) 7100 R-4 1,485 2,037 2,971 3,779 R-5 677 1,241 1,547 1,656 * L-1 = Left Thumb, L-2 = Left Index, L-3 -- Left Middle, L-4 = Left Ring, L-5 = Left Little, R-1 = Right Thumb, R-2 -- Right Index, R-3 = Right Middle, R-4 = Right Ring and R-5 = Right Little. TABLE II--AvEr. AGE CHANGES IN HARDNEss--PLACEBO REGIMEN Weight Load Nail Subject in Grams Sample* ß --Knoop Hardness Numbers---, Initial 1 Month 2 Months 5 Months R 7100 L-4 4,310 8,698 6,810 7,668 (Male) L-5 3,627 6,810 6,099 4,310 R-5 2,971 7,221 6,445 5,214 Q 7100 L-5 580 494 509 561 (Male) R-3 580 631 580 526 R-5 757 703 703 631 P 7100 L-5 2,037 1,805 1,704 1,525 (Male) R-3 1,805 2,037 1,805 1,805 R-5 1,805 1,446 1,610 2,320 O 7100 I,-5 6,445 7,221 6,810 5,781 (Male) R-3 4,210 5,214 4,120 3,495 R-5 8,158 10,650 6,810 9,273 H 6100 L-5 1,464 1,464 1,384 1,750 (Male) R-3 1,066 970 965 926 R-5 926 1,017 1,058 778 E 4100 L-4 2,007 2,182 2,009 1,854 (Female) L-5 2,092 2,379 2,279 2,092 R-5 1,253 1,108 1,141 1,141 D 4100 L-4 1,254 1,254 1,176 1,176 (Female) L-5 1,254 1,538 1,176 1,214 R-5 1,254 1,254 1,214 1,254 L 7100 L-3 25,539 15,783 15,783 20,860 (Male) L-5 3,088 3,341 3,088 3,475 R-5 68,898 68,898 49,466 58,121 * L-1 -- Left Thumb, L-2 = Left Index, L-3 -- Left Middle, L-4 = Left Ring, L-5 = Left Little, R-1 = Right Thumb, R-2 = Right Index, R-3 = Right Middle, R-4 = Right Ring and R-5 = Right Little.