Chapter 14 469 Trotter and Duggins13 ran a sensitive study among Caucasian children by having hair sent to them periodically at 1-year intervals starting with infants through puberty. This study was discontinued after 17 years because of dropouts. These scientists started with 15 infants each at 1 month (50 hairs) and 7 months (50 hairs) and summed these two data points to represent 100 hairs at age 1 (closer to one-half year). Then they measured 100 hairs taken from the vertex of each of these same 15 subjects at 2 years of age, with one additional child at age 2, and continued with these 16 children once per year until age 17. However, due to the high dropout rate beyond age 10 (only 10 children remained in the study), we have reservations about the conclusions that can be drawn beyond this threshold. This data up to 10 years of age are summarized in Table 7. Table 7. Average indices of 100 hairs at ~ 1-year intervals on the same 14 subjects for the first ten years of life (letters corresponding to respective subjects)13 Age A B C D E F G H I J K L M N 1** 74 66 77 74 84 75 85 80 77 77 70 70 84 76 2 61 62 71 65 73 66 76 79 71 70 65 66 73 73 3 64 65 67 65 76 66 82 77 74 72 63 63 69 72 4 70 67 70 60 76 69 78 77 73 76 63 63 78 73 5 70 67 69 65 73 70 81 74 75 77 58 59 80 72 6 71 67 75 64 75 70 81 75 82 74 59 63 79 74 7 68 63 74 62 75 70 85 79 85 80 62 62 78 80 8 68 62 74 65 79 66 80 81 85 73 63 63 83 81 9 67 66 74 63 81 67 80 81 84 77 61 67 83 73 10 67 61 75 59 78 71 80 81 83 81 58 61 84 73 **One year measurements consist of 50 hairs taken at 1 month and another 50 at 7 months from each subject. These two measurements were averaged together. One year represents the hair closer to 4 months than to a full year. All other measurements were taken on 100 hairs per subject at the designated age. Trotter listed more subjects who dropped out at different times and have been deleted from this table. Not counting the 1 month and 7 month sampling, Trotter and Duggins had collected yearly data points measuring 100 hairs from each of 14 subjects from age “1” through age 10, commenting on