In the ancient world, care for the sick was presumed to be the domain of the family home. The hospital system developed for care of travelers, orphans, and the very poor. The words “hospital” and “hostel” are cognates, both derived from Latin “hospitium.” For a time, the medieval English word for a hospital was simply “spital.”
The first European hospitals were designated sick bays in Roman army camps. In a sense, every soldier was a traveler and an orphan (except for those whose sisters or mothers came along). If the army was to take a man from his family for years, it had to create a substitute sick care system. After the fall of the western empire, the Roman idea of dedicated houses for the sick persisted in its eastern capital, Constantinople. If you wanted to try out one of Paul of Aegina’s surgery methods, your best bet would be one of those Byzantine hospitals, where one could recover from an infection or have simple surgeries.
The next major hospital development was the growth of Benedictine monasteries in Europe. The Order of St. Benedict required rooms set aside for the sick, with a monk assigned to care for them. Monasteries grew medicinal herbs for the sick, and they also made sure that regular meals and baths were given. The sick were exempted from fasting; they could eat meat soup during Lent. (People being what they are, quite a few monks got sick during Lent.)
The monasteries primarily cared for their own sick and aged, especially the aged. Joining a monastery was a way of ensuring that you’d have nursing care in your last years. But the monasteries were also required to give care to travelers who fell sick, and to the local poor who were sick and aged. Gradually, some of the monasteries expanded their hospital functions to be more general.
A big turning point came with the Crusades, when Europeans got to see Constantinople’s hospital system. The idea of having dedicated places for the old, poor, and sick came home with Crusaders, who then supported hospitals with endowments. The first main group to bring the idea back was, of course, the Knights of the Hospital. Their original purpose was to guard pilgrims to Jerusalem by providing defensible houses with a few knights and men at arms attached. The Knights of the Hospital were a military-monastic order, so some of their number mainly fought in the Crusade wars. But others developed the function of the hostel/hospital in imitation of the Byzantine customs, and they began to spread Hospitaler houses into Europe. The first Hospitaler hospital in England began in 1128.
Other religious orders were founded specifically to care for the sick and poor, and many of them started in the Holy Land on the same model as the Hospitalers. The Order of St. Lazarus of Jerusalem cared for lepers. St. Mary of Bethlehem cared for, among others, the insane, and its institution in London became known as the infamous “Bedlam” short for Bethlehem. The Order of the Trinity administered hospitals in France, and a small order of St. Thomas the Martyr of Acon managed one large hospital in England.
Cities began to found hospitals with specific purposes. Some were for the blind, or for orphans, while others were for the aged. Most of them shunned infectious disease, since it was dangerous and there was at least enough physical frailty to keep their rooms full without it. Most of the charters included or excluded other conditions: pregnancy, leprosy, insanity. The most numerous and best city hospitals were in Italy, where each city-commune organized fairly efficiently at a time when the rest of Europe was primarily feudal. Guilds, too, founded hospitals for the sick and aged among their members.
The hospital at this time did a few basic things for its patients. First, it gave them a bed: literally a bed, perhaps the first bed the patient had ever seen. The rooms were heated and sometimes had lights burning at night. The patients got regular meals and baths. For many sick people, this was enough to recover. Second, it gave them spiritual care, which was seen as a key service in medieval times. The sick so often did not recover, and to die unconfessed meant spending much more time in Purgatory. So the monks and nuns who staffed the hospitals kept up regular prayers and masses, and patients were required to participate if at all able. Dying in a hospital meant almost certainly having the benefit of the last rites, which gave the dying some peace of mind, easing their pain.