The most extensive investigations have dealt with the first type discovered, namely the vitamine "B" or Funk antineuritic type. In 1911 Cooper and Funk found that the alcoholic extract of rice polishings could be precipitated with phosphotungstic acid and that this procedure permitted them to obtain a fraction that was particularly potent and free from proteins, carbohydrates, and phosphorus. Funk carried this investigation farther and fractioned the phosphotungstic acid precipitate with silver nitrate, following the usual procedure for separating nitrogenous bases. From the silver-nitrate baryta fraction he obtained a crystalline complex melting at 233°C. to which he gave the formula C_17H_20O_7N_2. This substance was curative for pigeons and the fractioning process was applied by him to yeast and other foodstuffs with similar results. From these results Funk believed the vitamine to belong to a class of substances known as the pyrimidine bases. Later, when working with Drummond, Funk was forced to admit that his crystalline complex was not the pure substance, as analysis showed that it contained large amounts of nicotinic acid. His product might well be considered as nicotinic acid contaminated with vitamines. Suzuki, Shimamura and Odake also used the phosphotungstic precipitation method and claimed to have prepared the crystalline antineuritic substance which they called oryzanin in the form of a crystalline picrate. Drummond and Funk repeated this work, but were unable to confirm the Japanese results. A group of British chemists (Edie, Evans, Moore, Simpson and Webster) obtained an active fraction from yeast and succeeded in separating this into a crystalline basic member belonging to the pyrimidine group which they called _torulin_. None of these three preparations have stood the test of analysis however and their curative properties seem to lie in their greater or less contamination with the actual substance, whatever it is. Numerous modifications of the fundamental method for extracting the substance have been planned and executed. Funk for example has shown that if the phosphotungstic precipitate is treated with acetone it is possible to separate it into an acetone soluble and an acetone-insoluble fraction and that the curative fraction is in the latter. McCollum has reported that while ether, benzene and acetone cannot be used to extract the B vitamine from its source, benzene, (and to a slight extent acetone) will dissolve the vitamine if it is first deposited from an alcohol extract on dextrin. These observations have not yielded any further clew to the nature of the substance.