Scurvy supplies a clear illustration available to an 1864 candidate: an appropriate change in diet can act as a remedy. In A Treatise of the Scurvy by James Lind, James Lind described a shipboard comparison begun on 20 May 1747. Twelve affected sailors lived in the same sick quarters and shared a common basic diet, while pairs received different additions. The additions included cider, acidic preparations, sea water, a compound preparation, and fresh oranges and lemons. Thus the comparison asked whether a particular addition helped, rather than merely observing that patients ate while recovering.
The pair given fresh citrus each received two oranges and one lemon daily. Supplies lasted six days. James Lind reported that one was then fit for duty, while the other had recovered sufficiently to help nurse the remaining sick. The exact contrast matters: two recoveries are not proof that every sour substance is equivalent to citrus, and James Lind's physiological theories should not be confused with the observed result. The record is also a small comparison with incompletely specified allocation, rather than evidence for a modern randomized design. It nevertheless supplies a concrete, pre-1864 illustration of a therapeutic resource carried in food. [ref]
A Treatise of the Scurvy by James Lind. 1753, pp. 191–196, common diet, six paired treatments and the course of the citrus recipients; original pages reproduced by the James Lind Library
Present explanation. Scurvy is caused by deficient vitamin C intake. Humans require a dietary source of vitamin C; it is needed for normal collagen formation. Deficiency weakens connective tissue and can produce fragile small blood vessels, bleeding gums and poor wound healing. Suitable food can therefore correct the deficiency, not merely disguise its symptoms. This explanation is later knowledge: an 1864 candidate could cite the effect of fresh antiscorbutic food without knowing the chemical identity of vitamin C. The effective factor is not simply acidity, nor is the claim that more vitamin C cures every unrelated disease. [ref]
Vitamin C Fact Sheet for Health Professionals by NIH. Introduction, Vitamin C Deficiency and Food Sources: dietary requirement, collagen, scurvy and citrus sources
There is also a broader nutritional sense. In malnutrition, adequate food supplies energy and protein needed for recovery, and the composition and route of nutritional support depend on the person's capacity to eat and absorb it. Current guidance distinguishes ordinary enriched food and oral supplements from enteral or parenteral support when required. This extends the principle of using nourishment therapeutically, while distinguishing it from a specific cure such as correcting vitamin C deficiency. These present-day care pathways are not attributed to ancient practice or to the 1864 examiner. [ref]