An institution in which certain kinds of illness are investigated and treated. The first documented hospital was Chinese, in 491. In the European Middle Ages the well-to-do were all treated at home, while the sick poor were cared for in a hospital attached to the local poor house. This pattern of care persisted into the 18th Century , when voluntary hospitals were built throughout the UK, and physicians and surgeons from the locality attended to the inmates without remuneration. With the advance of scientific medicine and the development of increasingly elaborate and specialized investigative and therapeutic procedures, all sections of the population whose medical needs might benefit from admission to hospital are now treated in hospital. In most developed countries today, hospitals are run as either private charities or public (state) institutions, with ‘teaching hospitals’ closely related to the research departments of neighbouring universities. Most hospitals not only cater for emergencies of all types and for those whose illnesses develop acutely and unexpectedly (the acute hospital), but they contain specialized departments for non-emergency work and for numerous branches of medicine, such as cardiology and neurology. Other hospitals have become exclusively specialized, and cater for the needs of single categories of ill health, such as psychiatric, orthopaedic, maternity, paediatric, and geriatric hospitals. An additional important role is the provision of out-patient departments providing consultative services for the patients of general practitioners who are under care in their own home. In the 1990s, in the UK, hospitals were allowed to opt out of local health authority control, forming themselves into hospital trusts (or NHS trusts), the others remaining as directly-managed units (DMUs).