1. Distinction of the threshold of judgment and the threshold of perception, as has been proposed by Professor Hukuda, is adopted and procedure of their determination is standardized under his guidance and instruction.
2. A method of point scoring and integration is introduced as the siandard procedure. Subjects are required to taste each 10 c. c. of sample solution with the whole mouth and allowed to think it over before deciding whether it has “no taste” “some undefinable or uncertain taste” (both scored as 0 point), “a definite but just definable taste”, which is right (scored as 3 points), “distinct taste” (scored as 4 points), “definitely stronger taste” (scored as 5 points). For each concentration three trials are made, and the sums (“a”s in Figg. 1 and 2) of points scored for each concentration are plotted against concentration (“C” in the figures) ; then the concentration correspoding to the level of 9 points is interpolated to define the threshold of perception technically (Cp), In Fig. 2 a perpendicular DS is placed so that the area ABR is equal to the area DSRB, which technically determines the position of S representing the threshold of judgment (Cj).
3. Effect of diferent system of scoring is also examined (Fig. 3) and discussed on.
4. Two alternative methods are tried and found to give about the same result as the procedure above mentioned. They are, however, inferior to the method of point scoring and integration, from theoretical or practical point of view.
5. Explanation of Tables :
Table 1: Threshold of perception in normal concentrations of 50 male adults for the taste of NaCl. Data for subjects Nos. 11-40 are omitted. I, II, ... V represent different systems of scoring. The numbers at the bottom are the averages of 50 subjects.
Table 2: Threshold of judgment of the same subjects as in the Table 1.
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