sentences:  Cow Tower formed part of the city defences during the 15th century, with the Crown occasionally issuing instructions that it should be repaired.In 1450 St Giles Hospital formally transferred any rights they had to the tower and the immediately surrounding land to the city.The population of Norwich grew significantly from 1500 onwards and the city continued to maintain the urban defences; like other towers and gatehouses belonging to the city, however, by this period the Cow Tower was probably leased out to a merchant or craftsman when not in military use.