None of the vitamines has been isolated in a pure state. The nearest approach to this desired end has been the work of Funk, who obtained the water-soluble vitamine in a state of such concentration that about 3 mg. sufficed to cure a pigeon of polyneuritis. In considering the attributes of the antiscorbutic vitamine, it must be borne in mind that this factor is referred to as it exists in various foods; for example, in orange juice or in cabbage, and furthermore, that the method of ascertaining its presence or concentration is limited to the crude biological test of animal feeding. The antiscorbutic factor is distinguished by being the most sensitive of the three vitamines, the most unstable, the least resistant to physical or chemical processes. It may be regarded as one of the most delicate indicators of the biological integrity of foodstuffs; however, as Falk and his co-workers have shown, the enzyme property of living matter is still more readily destroyed. The antiscorbutic vitamine is soluble in water, and therefore is termed by some the "water-soluble C" factor. It is also soluble in alcohol, as shown by the experiments of Hess and Unger and of Harden and Zilva, and the therapeutic tests on infants of Freise and of Freudenberg.[23] It possesses, therefore, the solubility of the water-soluble vitamine. Some have suggested that it may be derived from this vitamine, others that instead of one there may be a series of antiscorbutic factors--suggestions based on pure hypothesis. Holst and Froelich showed that this vitamine passes, without appreciable loss, through dialyzing parchment, and Harden and Zilva (2) that it can pass through a porcelain filter. The latter, using the method of Seidell, demonstrated that this vitamine is not adsorbed by fine precipitates such as fuller's earth, differing in this respect from the water-soluble vitamine; and that in a mixture of equal volumes of autolyzed yeast and orange juice, the antiscorbutic vitamine remained unaffected, whereas the water-soluble A was entirely removed. [23] Freise cured a case of infantile scurvy by giving about 2 c.c. of an extract obtained from turnips by means of absolute alcohol. Seven weeks were necessary to cause a disappearance of symptoms. Freudenberg employed an extract of carrots, prepared with 96 per cent. alcohol, and effected a quicker cure.