distance from the heart. He also correctly observed that the arteries contract when the heart expands and expand when the heart contracts. Lungs In describing the anatomy of the lungs, Ibn al-Nafis said: The lungs are composed of parts, one of which is the bronchi; the second, the branches of the arteria venosa; and the third, the branches of the vena arteriosa, all of them connected by loose porous flesh.....The need of the lungs for the vena arteriosa is to transport to it the blood that has been thinned and warmed in the heart, so that what seeps through the pores of the branches of this vessel into the alveoli of the lungs may mix with what there is of air therein and combine with it, the resultant composite becoming fit to be spirit when this mixing takes place in the left cavity of the heart. The mixture is carried to the left cavity by the arteria venosa. It is also found that "In the lungs, some blood was filtered through the two tunics (coverings) of the vessel that brought blood to the lungs from the heart. Ibn al-Nafīs called this vessel the ‘artery-like vein’, but we now call it the pulmonary artery." Brain Ibn al-Nafis was also one of the few physicians at the time, who supported the view that the brain, rather than the heart, was the organ responsible for thinking and sensation. Other medical contributions Practice of dissection There is some debate about whether or not Ibn al-Nafis participated in dissection to come to his conclusions about pulmonary circulation. Although he states in his writings that he was prevented from practicing dissection because of his beliefs, other scholars have noted that Ibn al-Nafis must have either practiced dissection or seen a human heart in order to come to his conclusions. According to one view, his knowledge about the human heart could have been derived from surgical operations rather than dissection. Other comments found in Ibn al-Nafis' writings such as dismissing earlier observations with a reference to dissection as proof, however, support the view that he practiced dissection in order to come to his conclusions about the human heart and pulmonary circulation. Ibn al-Nafis' comments to the contrary and the alternate explanations, however, keep his possible practice of dissection in question. During Ibn al-Nafis’ studies of the human body, dissection was prohibited by law in Islam, but was