Subsequent studies, carried out within the past few years, have served only to strengthen this viewpoint. For example, an "artificial orange juice" composed of the various salts, citric acid, and sucrose in the proportions in which they are found in the natural juice, failed, in the experience of Hess and Unger, to protect or to cure guinea-pigs--demonstrating that this preparation did not contain the essential factor. In the same way, Harden and Zilva were able to protect animals from scurvy with a preparation of lemon juice which had been almost entirely deprived of its salts. It is needless to multiply these examples. It is sufficient to state that there has been no investigation during the last years of intensive study of scurvy, which has tended to weaken the vitamine hypothesis. It may be stated, therefore, that experiments have demonstrated that scurvy is due essentially to the lack of a specific vitamine. It is unwise to proceed farther and place it in the group of so-called "deficiency diseases," including beriberi, pellagra, etc., unless the reservation is made that these several diseases may present marked differences. It is quite possible that one may be what might be termed a simple deficiency disease, whereas another may have important additional etiologic factors. At any rate, unless it is realized that there has been no proof that all are due to similar deficiencies, we may, by stamping them all alike and by grouping them together, be misled into taking their close relationship for granted. In regard to scurvy, there may well be other etiologic factors, but they are of a secondary character. Bacterial invasion has been referred to in this connection, and it is possible that toxins are absorbed from the intestine after nutrition has been disturbed. Diarrhoea and digestive disturbances may play a rôle. Whether the total intake of food or the correlation of its constituents--protein, carbohydrate, fat and salts--affects the action of the vitamine, is one which has not been well studied clinically or experimentally. In regard to beriberi, it is claimed that there is a direct ratio between the quantity of carbohydrate ingested and the amount of vitamine required. No such interrelationship exists in regard to scurvy. This was evident a few years ago (1917) when some infants receiving pasteurized milk, prepared with the addition of 3 per cent. flour, did not tend to develop scurvy more readily than others receiving simple pasteurized milk. A consideration of the antiscorbutic vitamine will be postponed for a subsequent chapter.