Let us return now to Harvey's polemic. In it he does not give chapter and verse by which we can properly verify more than a few of his statements of the views of "Scaliger, Fernelius, and others"; but the words of Aristotle which Harvey quotes go far to justify his intimation that the views which he states and combats, as the champion of the circulating blood, are largely derived from those Aristotelian words--whether by misinterpretation, as he roundly but indefinitely declares, or with deliberate modification of doctrine, need not now concern us. At the very outset of Harvey's discourse about the innate heat, the first doctrine that he reprobates is a striking one, viz.: that the innate heat is one and the same thing with spirits distinguishable from the blood, though not separable from it. Of these spirits he stoutly denies the existence, on the true scientific ground of lack of all evidence from observation in their favor. Our earlier studies of ancient doctrines of respiration have brought before us, as supposed to exist in the blood, spirits variously styled "elemental," "aërial," "nourished by our common and elemental air," "nourished and increased from the thinner part of the blood." We have even read Galen's words of spirits which are "the soul's most immediate instrument," viz.: the "animal spirits" in the brain and nerves. Indeed, during the eighteen centuries between the death of Aristotle and the boyhood of Fernelius and Scaliger, the word "_pneuma_"--"spirits" or "spirit"--did most varied duties in the service of physicians, philosophers, alchemists, and theologians; and this same word is of great importance in the scriptures.[345] It is noticeable that, although Harvey rejects the doctrine of spirits in the blood, even he himself talks of the blood being itself spirits.[346] This fact, however, should not militate against him or lead to confusion. The word "spirits" being a very comprehensive technical term of his day, he does not refuse to employ it as a label for qualities of the blood after he has denied the very existence of what is properly denoted by the word "spirits." He simply behaves as we behave when we talk of the "sympathetic" nerves, though the theory is exploded which the adjective expresses; or when we speak of "animal cell," well knowing that no proper wall necessarily surrounds the living substance.