LVII. The second argument, is built on the correspondence of the four humours of the body, with the four Aristotelic elements; that is to say, the blood with the air, the choler with the fire, the melancholy with the earth, and the pituitous with the water. But this puts us in a worse situation than we were before. In the first place, it is a doubt among the medical people, whether the humours of our bodies consist precisely of four. Some say they are more, and others that they are less. Some add to the four, the lymph, the pancreatic juice, and the nervous fluid; and some again will not admit, that there is any other humour except the blood. Secondly, if the four elements correspond only with the four humours, we are left without an element to correspond with the solids, which on account of the hardness of their substance, might with more propriety be compared to the earth, than to the melancholy humour, which is beyond comparison less hard and solid than the other. Thirdly, in the same voluntary manner, with which they assign four elements to correspond with the four humours, they may assign one element to correspond with the flesh, another with the bones, another with the marrow, another with the fat, or adipose substance, another with the tendons, and so on. Fourthly, in order to reason justly upon the human body, or animal species, we should not seek for four substances that are analogous to the four humours, but for four that enter into all the mixtures; for the question, relates to elements that partake of the composition of all mixtures in general, and not precisely of the animal. But what traces can we discern, of four humours, or four substances, equivalent to these, either in minerals, or plants? LVIII. The third argument in support of this quaternian system, is pretended to be derived from experience; for it is alledged, that when a piece of wood is burning, we see it resolve itself into the four Aristotelic elements. At first it emits a small portion of water; then it takes fire; the fire is followed by smoke, which we know to be of an aerial nature, by its ascending to the airy region; and last of all, there remains a portion of earth in the ashes.