The fats, like the carbohydrates, are composed of carbon, hydrogen and oxygen, but with these elements in very different proportions from that in which they exist in the carbohydrates. There is a much larger proportion of carbon with less oxygen than in starch and sugar, and this accounts for the readiness with which they burn and the intense heat that we get from them. They are of both animal and vegetable origin. Those which are liquid at ordinary temperature we often speak of as oils.