Another theory which had a short but popular career was the _citric acid theory_, which was maintained vigorously by Netter. This explanation seemed logical in view of the marked potency of the citrous fruits, and particularly when it was shown that human milk contains a greater percentage of the salts of citric acid than cow's milk, and that some of these salts are lost in the course of heating. This hypothesis withstood neither the practical test nor chemical investigation. It was found that the various salts of citric acid, either singly or in combination, are unable to cure scurvy. This treatment has been employed repeatedly on man and on animals with little or no success; we also have resorted to it in vain. It was shown, furthermore, that it rested on an insecure chemical basis, as boiled milk contains but 0.1 g. per litre less citric acid than raw milk--an amount which is negligible from a therapeutic point of view. Before considering what may be termed the prevailing theories, a few lines must be devoted to the _acidosis theory_ championed by Sir Almroth Wright. According to this writer scurvy is due primarily to an excess of acid compared with alkaline food.[5] A theory of this nature was open to verification, and soon collapsed when put to the test. It was found, in the first place, that an addition of alkali was unable to cure experimental scurvy. It may be added that we have found it of no value in infantile scurvy. Holst and Froelich pointed out that potatoes and peas, two excellent antiscorbutic vegetables, have an alkaline and not an acid ash; that adding hydrochloric acid to dandelion juice improves rather than diminishes its potency; that 1 g. of cabbage, which suffices to protect a guinea-pig from scurvy, does not contain sufficient alkali to neutralize an acid state; and, finally, that scurvy is not encountered in the well-established acidosis of diabetes. [5] The cases on which Wright based his theory were soldiers who developed scurvy during the siege of Ladysmith. It is probable that the men were suffering from starvation, purpura and dysentery. That they did not have scurvy is proved by the fact that they were cured by giving lactate and bicarbonate of soda. Let us turn to some of the current theories of the etiology of scurvy. For years many have held to the _toxic theory_, believing that poisons either were consumed in the food or formed in the intestine by means of bacterial action. At present this view is held by the minority. The situation in this respect may be compared to that of beriberi, about which there is also no consensus of opinion, a minority attributing it to the action of an unknown toxin.