Opus Majus of Roger Bacon, Vol. II (Burke English trans.)

is in the heart. But Avicenna, in the first book of his Canon of Medicine Original: "Art of Medicine", says that although the opinion of physicians is the most obvious to the senses, the opinion of the Philosopher Referring to Aristotle is the truer one. This is because all nerves, veins, and faculties of the soul originate first of all in the heart, as Aristotle proves in the twelfth book of his work On Animals, and as Avicenna also confirms in the third book of the same subject.