The Black Death (bubonic plague) reached Al Andalus in the 14th century. Ibn Khatima thought infectious diseases were caused by "minute bodies" which enter the human body and cause disease. Another Andalusian-Arabian physician, Ibn al-Khatib (1313–1374) in his treatise "On the Plague" stated how infectious disease can be transmitted through bodily contact and "through garments, vessels and earrings". Girolamo Fracastoro from Verona suggested these very small, unseeable, particles that cause disease were alive. They were able to spread by air, and multiply. They could be destroyed by fire. He refuted Galen's miasma theory (poison gas in sick people). In 1543, Fracastoro's book "De contagione et contagiosis morbis" suggested personal and environmental hygiene to prevent disease. The development of a sufficiently powerful microscope by Anton van Leeuwenhoek in 1675 provided visual evidence of living particles consistent with a germ theory of disease.