The first part of the work consists of thiamine analysis of 5 allotments of rice samples bought from retail shops in various districts in Canton from the end of 1954 to the beginning of 1957. Usually seven grades of rice are available, and the grades differ both in variety and extraction rate.It is found that the thiamine content of rice bought at the same time, or of the same grade bought within a few months may vary considerably. Two-third of the samples contain 0.11 to 0.18 mg of thiamine per 100 g of rice but it takes the range of 0.05 to 0.27 mg per 100 g to cover all the samples. With the exception of the lowest grade, the thiamine content in general increases with the lowering of grade and decrease of price.The second part of the work studies the influence of variety and of extraction rate upon the thiamine, niacin, riboflavin and protein content of rice. Seven varieties of rice commonly used for the seven grades extracted at different rates are obtained from a local rice mill by special arrangement with the City Food Bureau. 'Results show that milling decreases the content of these 3 vitamins and of protein, the decrease for thiamine and niacin being greater than for the other two nutrients. However, not only the original content of these nutrients in husked rice may vary, but also their degree of loss in milling may differ. Of the varieties studied the lowest grade of husked rice contains the greatest amounts of all the four nutrients while the "Super Grade A" tends to lose the least during milling. As a result, the milled products of these two varieties tend to contain slightly larger quantities of these nutrients.

This study is undertaken simultaneously with the experiments for the determination of riboflavin requirement of middle school boys in Canton. The same subjects serve in both experiments. When the loading tests are performed, 2.0 mg of thiamine is given orally at the same time the riboflavin is administered. Supplements of 0.5, 1.0 and 1.5 mg thiamine are given at the same time and in the same order as the ribofiavin. The same urine samples are analyzed for thiamine as well as riboflavin. Thiamine is analyzed by the thiochrome method of Consolazio.The thiamine content in the one-hour urine samples of the subjects before the supplement averages 5.4 to 8.9 micrograms for the 4 groups. After supplementation, the thiamine content of the fasting samples of 1.0 and 1.5 mg supplement groups show definite increase, while the other two groups remain near the same levels.After the loading test, the 4-hour total excretion amounts to about 5 per cent of the 2 mg taken, with almost no difference among the groups. When the intake of thiamine has been supplemented for two weeks, the response to the loading test varies. The 0.5 mg supplemented group excreted 4.35% of 2 mg in 4 hours, while the 1.0 and the 1.5 mg groups excreted about 8%. The hourly excretions are shown in Fig. 1. The peak of excretion of the 1.5 mg supplemented group changes from the second to the first hour after the load test. The thiamine intake of these subjects is estimated to be about 1 mg daily. They are free from symptoms associated with thiamine deficiency and their 1-hour urine samples show that the quantity excreted may be within the range considered normal for healthy subjects, yet supplementation of 1.0 or 1.5 mg of thiamine is able to cause a greater and faster urinary excretion of thiamine. An additional intake of at least 1.0-1.5 mg thiamine to their ordinary dietary intake of about 1 mg may be desirable to ensure an optimum status of thiamine nutrition in the middle school boys.