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258 aorta;" the anatomy is, no doubt, imperfect, but it still is an outline of the knowledge of the lacteals. It seems to shew that veins gather fluid from the intestines, and convey it to the large blood vessels; but there was no analogous knowledge, in that age, whereby the process of decay that is absorption could be accounted for. The term decay, therefore, was the mere expression for a general fact.

The objection to the terms "upwards and downwards," used by Empedocles to delineate the growth of plants, suggests the advantage that would accrue to science, if its terms were made sufficiently precise to fix, beyond doubt, the several relations and positions of the same body, or all bodies. And in the analogy between the heads of animals and roots of trees, we cannot but perceive the outline of a doctrine which has been developed, by modern science, into homologous physiology.

Note 4, p. 79. The nature of fire seems to some philosophers, &c.] This is an argument, drawn from the agency of fire, to disprove the then prevailing opinion, that, as it alone of the elements appears to be nourished and to grow, it may be the source of life and the origin of living actions; as they are shewn, by the contrast between living and igneous properties, to be essentially distinct from one another. The opinion may have originated from the fact that heat accompanies digestion, and as fire was by some held to be the first element, it was readily supposed to be the agent in that process. As