These are remedies which are useful in the counteraction of Scurvy and Purpura. In these disorders there is a thin and poor condition of the blood, together with a deficiency in the amount of albumen, fibrine, and the solids generally; a tendency to hæmorrhages and ulcerations, consequent on this condition of the blood; and great general depression and debility. There is no doubt that these changes in the blood are due to a certain morbid action. It seems that there are some kinds of food which are able to prevent the occurrence of this morbid action, or to control it when it has been set up. The worst forms of Scurvy occur among sailors in long voyages, who have been deprived for some time of fresh vegetable food; and it is often observed that those who have been thus afflicted on land have been subjected to the same deprivation. But it does not follow as a matter of course that those who are thus deprived become invariably the victims of Scurvy. It seems that there are certain constitutions which are more disposed to it than others; and that when these systems are deprived of some articles of diet which are able to prevent or to neutralize the working of the poison in them, the latent morbid action is allowed to commence. Of all the substances of which trial has been made, Lemon or Lime juice, and Potatoes, are said to be of the greatest use in the treatment of scurvy. The former is generally employed on board ships. These both contain Citric acid and salts of potash. But the chief agent in the cure should be something which is not contained in the food eaten by those who are commonly attacked with Scurvy. The food of the sailors who are thus afflicted consists mainly of salted beef and sea-biscuit. Both contain salts of Potash; neither contain Citric acid. So that from this consideration it would seem as if the free acid must be the remedial agent. Vegetables in their fresh state generally contain a small quantity of this or some other acid; and fresh vegetable food is always the best prophylactic against Scurvy and Purpuric diseases. Various wild herbs, some of which contain Oxalic instead of Citric acid, are used among the poor for this purpose.[41] Dr. A. B. Garrod is of opinion that Scurvy is attributable to a deficiency in the system of the natural amount of the salts of Potash; he therefore treats it with salts of Potash, and apparently with success. (_Monthly Journal of Medicine_, January, 1848.) The salts of Potash, if used on such grounds, would obviously act as Restorative agents, and supply to the blood a material in which it is deficient. But Citric acid could not remain in the blood; and if it cures Scurvy, it must act on the Catalytic principle. It could not supply to the system any permanent material.