"It assuredly contains the soul first and foremost, not only the nutritive, but the sensory soul as well, and the motor. The blood penetrates in all directions and is present everywhere; if it be taken away, the soul itself is made away with also and at once; so that the blood would seem to be wholly indistinguishable from the soul or, at least, should be reckoned the substance of which the soul is the activity. The soul I aver to be such that neither is it body at all, nor yet entirely without body, but comes in part from without, in part is born on the premises,[281] and in a manner is part of the body; in a manner, however, is the origin and cause of everything within the body of an animal, certainly of nutrition, sense, and motion, and hence, in like manner, of life and death; for whatsoever is nourished, that same is living, and vice versa. So, likewise, whatsoever is nourished abundantly, increases; but whatsoever too sparingly, dwindles; and whatsoever is nourished perfectly, keeps its health; whatsoever otherwise, lapses into disease. Therefore, as is the soul, so also is the blood to be reckoned the cause and author of youth and old age, of sleep and of waking, and even of respiration also—especially in view of this, that in the things of nature the first instrument contains within itself an internal moving cause. Therefore, it comes to the same whether one say that the soul and the blood, or the blood together with the soul, or, if preferred, the soul together with the blood, bring everything within an animal to pass."[282]
Only two years before these words were published the aged Harvey had said the following:—
"Nor does the blood possess vigor, faculty, reason, motion, or heat, as the gift of the heart."[283]
A comparison of the foregoing passages from Harvey with the preceding passages from Aristotle makes it clear that, for Harvey, although the soul dwells no longer in its Aristotelian seat, it is no other than the Aristotelian soul which pervades the "principal part" of the body, the living blood of the Harveian circulation.
What proofs does Harvey offer that the soul is in the blood? He has offered already one weighty piece of evidence noted by many from of old in the chase, in butchery, in sacrifice, in battle—the evidence from fatal hæmorrhage. This had been set forth nineteen centuries before him by one of his Hippocratic predecessors, who had referred to the reasoning
"used by those who say that the blood is the man; for, seeing men slaughtered and the blood running out of the body, they conclude that the blood is the soul of man."[284]
Presently Harvey himself shall tell us that in placing the soul in the blood he is consciously reaffirming one of the most ancient of beliefs; but he is far from basing his adhesion to it merely on such immemorial evidence, known to all, as the result of loss of blood, for he also adduces once more his own observations of the early embryo of the fowl, to prove not only the primacy of the blood but the presence of the soul therein. His testimony follows, and in reading it one must bear carefully in mind that in Harvey's time no clear scientific distinction had yet been worked out between movements which imply sensation, and movements, whether reflex or not, which do not depend upon consciousness. In his treatise On Generation Harvey says:—
"For my own part I am sure from numerous experiments that not only motion is inherent in the leaping point,—which no one denies—but sensation also. For you will see this point thrown into varied commotion and, as it were, irritated, at any touch whatever, even the slightest, just as sensitive bodies in general usually give evidence of sensation by movements proper to themselves. Moreover, if the injury be repeated often, the leaping point becomes excited and the rhythm and order of its pulsations disturbed. In like manner do we infer the presence of sensation in the so-called sensitive plant and in zoöphytes, from the fact that when they are touched they draw themselves together as though taking it ill.... So there is no doubt that the leaping point lives, moves, and feels like an animal."[285]
In a later part of the same treatise he says:—
"It is manifest that all motion and sensation do not proceed from the brain, since we plainly perceive the presence of motion and sensation before the brain has come into existence; what I have related proves that clearly sensation and motion dawn forthwith in the first droplet of blood in the egg, before a vestige of the body has been formed. Moreover, in that first state of the structure or constitution of the body which I have called the mucilaginous, before any members are discernible and when the brain is nothing but limpid water, if the body be only lightly pricked it moves, contracts, and twists itself obscurely like a worm or caterpillar; so that it gives clear evidence of sensation."[286]