Surprisingly to me, for an educated man of his time, Dana gives no indication of knowing the cause of scurvy. He mentioned it a couple times before, with no sign of understanding it at all. Here he is describing crew of a Russian vessel he visited in San Francisco harbor:
"To a Russian, grease is the greatest luxury. They looked with greedy eyes upon the tallow-bags as they were taken into the vessel, and, no doubt, would have eaten one up whole, had not the officer kept watch over it. The grease seemed actually coming through their pores, and out in their hair, and on their faces. It seems as if it were this saturation which makes them stand cold and rain so well. If they were to go into a warm climate, they would all die of the scurvy."
He had mentioned "grease" comprising too much of their diet, but show no comprehension of value of fruits and vegetables.