Complex sentence: Capillary circulation was not known in Europe for several centuries until Marcello Malpighi in 1661, though Ibn al-Nafis' theory was confined to blood transit in the lungs and did not extend to the entire body.
Split into simpler sentences: Capillary circulation was not known in Europe for several centuries until Marcello Malpighi in 1661. However, al-Nafis' theory was confined to blood transit in the lungs; it did not extend to the entire body.