caused by the motion of blood through arteries, as evidenced by the Cyclopaedia (1728): "For 'tis hence we know, that this innate Heat is no more than the Attrition of the Parts of the Blood; occasion'd by its circulatory Motion, especially in the Arteries." Aristotle's views Aristotle believed that the source of vital heat lies in the heart and is intimately connected to the soul. "This link is not for Aristotle simply an accidental connection, but rather the existence of vital heat is necessitated by the most basic living activity: nutrition. In De anima ii 4.416b28-29, Aristotle says: 'All food must be capable of being digested, and that whose activity causes digestion is heat. For this reason, every animate thing has heat.'". Although prominent scholars like Aristotle accepted this concept of innate heat and its role in digestion, there were others who were skeptical and retained a different point of view. "However, if we look for antecedents of Aristotle's theories, the most important are probably to found in the Timaeus. Here Plato shows in some detail how in respiration the 'Hot' in us is cooled by the air which enters from outside, and he relies on the cutting power of the fire, which here is identical to the 'Hot', to explain the process of digestion Along with his theory of the role of vital heat in nutrition and digestion, Aristotle believed that vital heat played a role in reproduction which includes several physical parts of the body different from the parts that participate in nutrition. Aristotle believed that blood was created through the process of digestion via vital heat and then pushed to the extremities of the body. However, blood is not in its final form but is transformed to a final substance to be used for the nourishment of the body. "Aristotle holds that semen is nutriment in its final stage of concoction before it becomes part of the body. Hence, blood, before it turns into flesh, bones, etc., first turns into semen." Although blood is not in its final form, it can still be used to nourish the body and create flesh and bone. "Young males do not have semen because the conversion into flesh and bone must be done quickly owing to their rapid growth. And women do not have semen because they are not as hot as men and so lack the power of concocting blood