XXX. A brief examination of the construction of our bodies from a medical point of view.
24 Now this force is that which is considered as residing in the cerebral membranes and the brain, from which it comes that every movement of a joint, every contraction of the muscles, every spontaneous influence that is exerted upon the individual members, renders our earthen statue active and mobile as though by some mechanism. For the most pure form of heat and the most subtle form of liquid, being united by their respective forces through a process of mixture and combination, nourish and sustain by their moisture the brain, and hence in turn, being rarefied to the most pure condition, the exhalation that proceeds from that organ anoints the membrane which encloses the brain, which, reaching from above downwards like a pipe, extending through the successive vertebræ, is (itself and the marrow which is contained in it) conterminous with the base of the spine, itself giving like a charioteer the impulse and power to all the meeting-points of bones and joints, and to the branches of the muscles, for the motion or rest of the particular parts.
25. For this cause too it seems to me that it has been granted a more secure defence, being distinguished, in the head, by a double shelter of bones round about, and in the vertebræ of the neck by the bulwarks formed by the projections of the spine as well as by the diversified interlacings of the very form of those vertebræ, by which it is kept in freedom from all harm, enjoying safety by the defence that surrounds it.
26. So too one might suppose of the heart, that it is itself like some safe house fitted with the most solid defences, fortified by the enclosing walls of the bones round about; for in rear there is the spine, strengthened on either side by the shoulder-blades, and on each flank the enfolding position of the ribs makes that which is in the midst between them difficult to injure; while in front the breast-bone and the juncture of the collar-bone serve as a defence, that its safety may be guarded at all points from external causes of danger.
27. As we see in husbandry, when the rain fall from the clouds or the overflow from the river channels causes the land beneath it to be saturated with moisture (let us suppose for our argument a garden, nourishing within its own compass countless varieties of trees, and all the forms of plants that grow from the ground, and whereof we contemplate the figure, quality, and individuality in great variety of detail); then, as these are nourished by the liquid element while they are in one spot, the power which supplies moisture to each individual among them is one in nature; but the individuality of the plants so nourished changes the liquid element into different qualities; for the same substance becomes bitter in wormwood, and is changed into a deadly juice in hemlock, and becomes different in different other plants, in saffron, in balsam, in the poppy: for in one it becomes hot, in another cold, in another it obtains the middle quality: and in laurel and mastick it is scented, and in the fig and the pear it is sweetened, and by passing through the vine it is turned into the grape and into wine; while the juice of the apple, the redness of the rose, the radiance of the lily, the blue of the violet, the purple of the hyacinthine dye, and all that we behold in the earth, arise from one and the same moisture, and are separated into so many varieties in respect of figure and aspect and quality; the same sort of wonder is wrought in the animated soil of our being by Nature, or rather by Nature's Lord. Bones, cartilages, veins, arteries, nerves, ligatures, flesh, skin, fat, hair, glands, nails, eyes, nostrils, ears—all such things as these, and countless others in addition, while separated from one another by various peculiarities, are nourished by the one form of nourishment in ways proper to their own nature, in the sense that the nourishment, when it is brought into close relation with any of the subjects, is also changed according to that to which it approaches, and becomes adapted and allied to the special nature of the part. For if it should be in the neighbourhood of the eye, it blends with the visual part and is appropriately distributed by the difference of the coats round the eye, among the single parts; or, if it flow to the auditory parts, it is mingled with the auscultatory nature, or if it is in the lip, it becomes lip; and it grows solid in bone, and grows soft in marrow, and is made tense with the sinew, and extended with the surface, and passes into the nails, and is fined down for the growth of the hair, by correspondent exhalations, producing hair that is somewhat curly or wavy if it makes its way through winding passages, while, if the course of the exhalations that go to form the hair lies straight, it renders the hair stiff and straight.
28. Our argument, however, has wandered far from its purpose, going deep into the works of nature, and endeavouring to describe how and from what materials our particular organs are formed, those, I mean, intended for life and for good life, and any other class which we included with these in our first division.
29. For our purpose was to show that the seminal cause of our constitution is neither a soul without body, nor a body without soul, but that, from animated and living bodies, it is generated at the first as a living and animate being, and that our humanity takes it and cherishes it like a nursling with the resources she herself possesses, and it thus grows on both sides and makes its growth manifest correspondingly in either part:— for it at once displays, by this artificial and scientific process of formation, the power of soul that is interwoven in it, appearing at first somewhat obscurely, but afterwards increasing in radiance concurrently with the perfecting of the work.
30. And as we may see with stone-carvers— for the artist's purpose is to produce in stone the figure of some animal; and with this in his mind, he first severs the stone from its kindred matter, and then, by chipping away the superfluous parts of it, advances somehow by the intermediate step of his first outline to the imitation which he has in his purpose, so that even an unskilled observer may, by what he sees, conjecture the aim of his art; again, by working at it, he brings it more nearly to the semblance of the object he has in view; lastly, producing in the material the perfect and finished figure, he brings his art to its conclusion, and that which a little before was a shapeless stone is a lion, or a man, or whatsoever it may be that the artist has made, not by the change of the material into the figure, but by the figure being wrought upon the material. If one supposes the like in the case of the soul he is not far from probability; for we say that Nature, the all-contriving, takes from its kindred matter the part that comes from the man, and moulds her statue within herself. And as the form follows upon the gradual working of the stone, at first somewhat indistinct, but more perfect after the completion of the work, so too in the moulding of its instrument the form of the soul is expressed in the substratum, incompletely in that which is still incomplete, perfect in that which is perfect; indeed it would have been perfect from the beginning had our nature not been maimed by evil. Thus our community in that generation which is subject to passion and of animal nature, brings it about that the Divine image does not at once shine forth at our formation, but brings man to perfection by a certain method and sequence, through those attributes of the soul which are material, and belong rather to the animal creation.
31. Some such doctrine as this the great apostle also teaches us in his Epistle to the Corinthians, when he says, “When I was a child, I spoke as a child, I understood as a child, I thought as a child; but when I became a man I put away childish things”; not that the soul which arises in the man is different from that which we know to be in the boy, and the childish intellect fails while the manly intellect takes its being in us; but that the same soul displays its imperfect condition in the one, its perfect state in the other.
Source: On the Making of Man (New Advent)