Ancient Roman medicine combined various techniques using different tools and rituals. Ancient Roman medicine included a number of specializations such as intemistic, ophthalmology and urology. Romans believed in supernatural causes for many diseases and in some supernatural cures (see bottom of article). The Romans favoured the prevention of diseases over the cures of them; unlike in Greek society where health was a personal matter, Public health was encouraged by the government at the time; they built bath houses and aqueducts to pipe water to the cities. Many of the larger cities, such as Rome, boasted an advanced sewage system, the likes of which would not be seen in the Western world again until the late 17th and 18th centuries. However, the Romans did not fully understand the involvement of germs in disease. Roman surgeons carried a tool kit which contained forceps, scalpels, catheters and arrow extractors. The tools had various uses and were boiled in hot water before each use.