Scurvy observed in any organism apart from humans and had been considered an exclusively human disease. Certain birds, mammals, and fish are susceptible to scurvy, but pigeons are unaffected, since they can synthesize ascorbic acid internally. Holst and Frølich found they could cure scurvy in guinea pigs with the addition of various fresh foods and extracts. This discovery of an animal experimental model for scurvy, which was made even before the essential idea of "vitamins" in foods had been put forward, has been called the single most important piece of vitamin C research. In 1915, New Zealand troops in the Gallipoli
Vitamin K deficiency thus activate) certain enzymes involved in coagulation: Factors II, VII, IX, X, and protein C and protein S. Inability to activate the clotting cascade via these factors leads to the bleeding symptoms mentioned above. Notably, when one examines the lab values in Vitamin K deficiency [see below] the prothrombin time is elevated, but the partial thromboplastin time is normal or only mildly prolonged. This may seem counterintuitive given that the deficiency leads to decreased activity in factors of both the intrinsic pathway (F-IX) which is monitored by PTT, as well as the extrinsic pathway (F-VII) which is monitored by PT.