Late stage can have open wounds, bleeding under the skin and the gums, and teeth falling out. End stage, scurvy, is associated with seizures and even death. The amount needed per day is not much.
In his list, Funk used the letter "C" to designate a factor still unidentified, but known to prevent scurvy. Later on, Szent Györgyi and Haworth chemically identified "C" as ascorbic acid ...