同一刺戟物に對する味覺的反應の個人的種族的差異

抄録

Since the previous paper was published elsewhere (vol.9, No.1, of this Journal) the writer has been able to extend the range of his work both as to number of persons tested and variety of locality, by which means he was enabled to obtain the reactions of about 7500 new subjects. The present paper is a report of a part of the results derived from the combined materials, new and old.
Using the chemical compound, para-ethoxy-phenyl-thio-carbamide, 8824 Japanese, 5933 Formosans (Chinese origin), 1756 natives (Formosan aborigines of various tribes) were tested and their reactions reported in writing or orally. In all races the reaction showed great individual divergences, some experiencing a bitter taste, others finding the compound sweet, sour, or salty, while by some no reaction was felt apart from tactual sensation. Roughly classified, the reactions may be said to fall into three categories-the tasteless, the bitter, and the others. The frequency proportion of the bitter reaction was the highest, the tasteless the next, and that of the others the lowest. This order was alike for all races.(cf: Tables I and II.)
The actual size of the frequency percentage for the same category, however, showed the existence of a great difference between the various races. The frequency percentage of the tasteless was found to be largest for the Japanese people, the figures for the Formosans were as small as about 50% of those for the Japanese, while those for the natives were less than one eighth of those for the first. Of the three native tribes, the Atyal has the largest ratio of non-tasters, though compared with that of other races it is very low; in the case of the other two native tribes it is almost negligible. The percentages of the bitter-tasters were found to be just the inverse of those for the non-tasters, in the same order of race, as given above, i. e. lowest for the Japanese and highest for the natives. As a matter of fact, the existence of the racial difference in respect of the frequency of non-tasters of the compoud-so also that of the bitter-tasters-is doubtlessly conclusive, and would appear to deserve more extensive and analytical investigation, for such a remarkable difference promises to lead to the discovery of some essential racial characteristic of service in the study of many important aspects of scientific and practical data when more carefully elaborated. The racial difference in the frequency of the sweet and other tasters, on the other hand, presented itself as insignificant when having regard for probable errors.(cf. Tables II, III, IV.)
In connection with these racial differences, some of the conditions which might be suspected as affecting the difference, and might often complicate or even lead to wrong conclusions in extreme cases, have been studied in so far as the statistical method is concerned. First: Comparing the percentages of the tasteless cases for the populations in the north, middle and the south of Formosa (average temperature: 21.6°, 22.1°, 23.1°C. respectively), no statistically significant difference was found, which suggests that no local influence affects the ratio.(cf. Table v.) Of course, since the local conditions possibly responsible for the ratio may be numerous and vary greatly, a decisive conclusion as to local influence in general has yet to be worked out. But it is demonstrated, in the present study at least, that no local influence capable of affecting the racial difference can be isolated. Second: Statistically significant differences in percentage among the tasteless was not found between the sexes of all the Japanese, Formosan and Atyal peoples.(cf. Table VI.) Moreover with the Japanese the sex difference in this category was statistically examined at age intervals of two years and the percentages of the non-tasters of the one sex was compared with that of the other in the corresponding age class.