In the early 18th century, the disease was seen as similar to smallpox, due to its analogous symptoms. The personal physician of the pope, Giovanni Maria Lancisi, recommended the destruction of all infected and exposed animals. This policy was not very popular and used only sparingly in the first part of the century. Later, it was used successfully in several countries, although it was sometimes seen as too costly or drastic, and depended on a strong central authority to be effective (which was notably lacking in the Dutch Republic). Because of these downsides, numerous attempts were made to inoculate animals against the disease. These attempts met with varying success, but the procedure was not widely used and was no longer practiced at all in 19th-century Western or Central Europe. Rinderpest was an immense problem, but inoculation was not a valid solution. In many cases, it caused too many losses. Even more importantly, it perpetuated the circulation of the virus in the cattle population. The pioneers of inoculation did contribute significantly to knowledge about infectious diseases. Their experiments confirmed the concepts of those who saw infectious diseases as caused by specific agents, and were the first to recognize maternally derived immunity.