The Hess test — the capillary fragility test — is an old clinical test for scurvy and other bleeding tendencies: a blood-pressure cuff is inflated on the arm to partially occlude venous return, or the skin is firmly pressed, and the examiner watches for the appearance of tiny broken capillaries (petechiae). In vitamin C deficiency, the capillary walls weaken from defective collagen, so they rupture under pressure that healthy vessels withstand. Before laboratory assays for ascorbic acid, this simple bedside manoeuvre helped diagnose scurvy in sailors, explorers, and the malnourished. Modern medicine has replaced it with blood tests, but it remains a neat illustration of how a nutrient deficiency announces itself in the body’s smallest vessels.