This fact is made particularly striking, when we find that neither is there a heart found in every animal, neither does it necessarily and in every instance pulsate at all times where it is encountered; the blood, however, or a fluid which stands in lieu of it, is never wanting.
EXERCISE THE FIFTY-SECOND.
Of the blood as prime element in the body.
It is unquestionable, then, and obvious to sense, that the blood is the first formed, and therefore the genital part of the embryo, and that it has all the attributes which have been ascribed to it in the preceding exercise. It is both the author and preserver of the body; it is the principal element moreover, and that in which the vital principle (anima) has its dwelling-place. Because, as already said, before there is any particle of the body obvious to sight, the blood is already extant, has already increased in quantity, “and palpitates within the veins,” as Aristotle expresses it,[276] “being moved hither and thither, and being the only humour that is distributed to every part of the animal body. The blood, moreover, is that alone which lives and is possessed of heat whilst life continues.”
And further, from its various motions in acceleration or retardation, in turbulence and strength, or debility, it is manifest that the blood perceives things that tend to injure by irritating, or to benefit by cherishing it. We therefore conclude that the blood lives of itself, and supplies its own nourishment; and that it depends in nowise upon any other part of the body, which is either prior to itself or of greater excellence and worth. On the contrary, the whole body, as posthumous to it, as added and appended as it were to it, depends on the blood, though this is not the place to prove the fact; I shall only say, with Aristotle,[277] that “The nature of the blood is the undoubted cause wherefore many things happen among animals, both as regards their tempers and their capacities.” To the blood, therefore, we may refer as the cause not only of life in general,—inasmuch as there is no other inherent or influxive heat that may be the immediate instrument of the living principle except the blood,—but also of longer or shorter life, of sleep and watching, of genius or aptitude, strength, &c. “For through its tenuity and purity,” says Aristotle in the same place, “animals are made wiser and have more noble senses; and in like manner they are more timid and courageous, or passionate and furious, as their blood is more dilute, or replete with dense fibres.”
Nor is the blood the author of life only, but, according to its diversities, the cause of health and disease likewise: so that poisons, which come from without, such as poisoned wounds, unless they infect the blood, occasion no mischief. Life and death, therefore, flow for us from the same spring. “If the blood becomes too diffluent,” says Aristotle,[278] “we fall sick; for it sometimes resolves itself into such a sanguinolent serum, that the body is covered with a bloody sweat; and if there be too great a loss of blood, life is gone.” And, indeed, not only do the parts of the body at all times become torpid when blood is lost, but if the loss be excessive, the animal necessarily dies. I do not think it requisite to quote any particular experiment in confirmation of these views: the whole subject would require to be treated specially.
The admirable circulation of the blood originally discovered by me, I have lived to see admitted by almost all; nor has aught as yet been urged against it by any one which has seemed greatly to require an answer. Wherefore I imagine that I shall perform a task not less new and useful than agreeable to philosophers and medical men, if I here briefly discourse of the causes and uses of the circulation, and expose other obscure matters respecting the blood; if I show, for instance, how much it concerns our welfare that by a wholesome and regulated diet we keep our blood pure and sweet. When I have accomplished this it will no longer, I trust, seem so improbable and absurd to any one as it did to Aristotle[279] in former times, that the blood should be viewed as the familiar divinity, as the soul itself of the body, which was the opinion of Critias and others, who maintained that the prime faculty of the living principle (anima) was to feel, and that this faculty inhered in the body in virtue of the nature of the blood. Thales, Diogenes, Heraclitus, Alcmæon, and others, held the blood to be the soul, because, by its nature, it had a faculty of motion.
Now that both sense and motion are in the blood is obvious from many indications, although Aristotle[280] denies the fact. And, indeed, when we see him, yielding to the force of truth, brought to admit that there is a vital principle even in the hypenemic egg; and in the spermatic fluid and blood a “certain divine something corresponding with the element of the stars,” and that it is vicarious of the Almighty Creator; and if the moderns be correct in their views when they say that the seminal fluid of animals emitted in coitu is alive, wherefore should we not, with like reason, affirm that there is a vital principle in the blood, and that when this is first ingested and nourished and moved, the vital spark is first struck and enkindled? Unquestionably the blood is that in which the vegetative and sensitive operations first proclaim themselves; that in which heat, the primary and immediate instrument of life, is innate; that which is the common bond between soul and body, and the vehicle by which life is conveyed into every particle of the organized being.
Besides, if it be matter of such difficulty to understand the spermatic fluid as we have found it, to fathom how through it the formation of the body is made to begin and proceed with such foresight, art, and divine intelligence, wherefore should we not, with equal propriety, admit an exalted nature in the blood, and think at least as highly of it as we have been led to do of the semen?—the rather, as this fluid is itself produced from the blood, as appears from the history of the egg; and the whole organized body not only derives its origin, as from a genital part, but even appears to owe its preservation to the blood.
We have, indeed, already said so much incidentally above, intending to speak on the subject more particularly at another time. Nor do I think that we are here to dispute whether it is strictly correct to speak of the blood as a part; some deny the propriety of such language, moved especially by the consideration that it is not sensible, and that it flows into all parts of the body to supply them with nourishment. For myself, however, I have discovered not a few things connected with the manner of generation which differ essentially from those motions which philosophers and medical writers generally either admit or reject. At this time I say no more on this point; but though I admit the blood to be without sensation, it does not follow that it should not form a portion, and even a very principal portion, of a body which is endowed with sensibility. For neither does the brain nor the spinal marrow, nor the crystalline or the vitreous humour of the eye, feel anything, though, by the common consent of all, philosophers and physicians alike, these are parts of the body. Aristotle placed the blood among the partes similares; Hippocrates, as the animal body according to him is made up of containing, contained, and impelling parts, of course reckoned the blood among the number of parts contained.