With such a varied dietary, comprehended in the above enumeration, it would be impossible for scurvy to invade the ship's company, especially when aided by other wholesome agencies, as cleanliness, well-ventilated and dry sleeping rooms, and clothing adapted to the weather. The antiscorbutic virtues of lime-juice were known long ago, being mentioned by {184} Albertus in 1593, but it was not until many years later that it became an integral part of the English navy-ration. The law requires it to be carried on board all merchant vessels, and to be served out ten days after the crew has been living on salt rations. The juice keeps well if properly prepared and preserved from contact with air, especially when fortified with a small quantity of alcohol, the usual strength being about 10 per cent. It should be carried in vessels containing just enough to furnish a few days' rations to the whole crew, by which plan only a small amount need be exposed to the decomposing influence of the air. The juice can be reduced by evaporation to a very small bulk. This method was adopted in supplying the Arctic cruiser Rodgers.[20] The juice was reduced to a paste, each pound of which represented one gallon of the solution of the ordinary strength. It has also been used in the form of lozenges and biscuit. It may be stated that great reliance has been placed upon malt, the acid wines, and cider as good antiscorbutics. [Footnote 20: _Report of the Surgeon-General of the Navy for 1880_.] In connection with the food-supplies it is proper to mention those influences of a depressing character which have a tendency to favor the development of scurvy. The first is dampness in the sleeping apartments of the men. This should be prevented by ventilation, drying stoves, and taking care that no wet garments are permitted to remain in the apartments. They should be taken off immediately and hung outside to dry, and under no circumstances should the men be permitted to sleep in them, as is sometimes done. Exposure to cold is unavoidable under certain conditions, and the men should then be protected by proper clothing adapted to the weather. Protracted fatigue is a third favoring circumstance, and the crew should be spared all the strain of hard work possible, especially in high latitudes. The apartments should also be kept well ventilated and scrupulously clean; and, lastly, depressing mental emotions, which are so apt to arise from exposure to danger and want, should be dispelled by cheering assurances, constant occupation, and whatever amusements can be had. These are the chief influences which are to be considered in adopting measures to prevent the occurrence of scurvy in communities, armies, on shipboard, or in persons confined in houses of detention.