tensions of collections of strings could do, and an exact practical acquaintance with the muscular cordage which exists in the animal frame ;in short, in this as in other instances of real advance in science, there must have been clear ideas and real facts, unity of thought and extent of observation, brought into contact.

Sect. 2.-Recognition of Final Causes in Physiology. Galen.

THERE is one idea which the researches of the physiologist and the anatomist so constantly force upon him, that he cannot help assuming it as one of the guides of his speculations; I mean, the idea of a purpose, or, as it is called in Aristotelian phrase, a final cause, in the arrangements of the animal frame. It is impossible to doubt that the motive nerves run along the limbs, in order that they may convey to the muscles the impulses of the will; and that the muscles are attached to the bones, in order that they may move and support them. This conviction prevails so steadily among anatomists, that even when the use of any part is altogether unknown, it is still taken for granted that it has some use. The developement of this conviction,-of a purpose in the parts of animals,-of a function to which each portion of the organization is subservient, contributed greatly to the progress of physiology; for it constantly urged men forwards in their researches respecting each organ, till some definite view of its purpose was obtained. The assumption of hypothetical final causes in Physics may have been, as Bacon asserts it to have been, prejudicial to science; but the assumption of unknown final causes in Physiology, has given rise to the science. The two branches of speculation, Physics and Physiology, were equally led, by every new phenomenon, to ask their question, "Why?" But, in the former case, "why" meant "through what cause?" in the latter, "for what end?" And though it may be possible to introduce into physiology the doctrine of efficient causes, such a step can never obliterate the obligations which the science owes to the pervading conception of a purpose contained in all organization.

This conception makes its appearance very early. Indeed, without any special study of our structure, the thought, that we are fearfully and wonderfully made, forces itself upon men, with a mysterious impressiveness, as a suggestion of our Maker. In this bearing, the thought is developed to a considerable extent in the well-known passage in Xenophon's Conversations of Socrates. Nor did it ever lose its hold on sober-minded and instructed men. The Epicureans, indeed,

held that the eye was not made for seeing, nor the ear for hearing ; and Asclepiades, whom we have already mentioned as an impudent pretender, adopted this wild dogma.15 Such assertions required no labor. "It is easy," says Galen," "for people like Asclepiades, when they come to any difficulty, to say that Nature has worked to no purpose." The great anatomist himself pursues his subject in a very different temper. In a well-known passage, he breaks out into an enthusiastic scorn of the folly of the atheistical notions." "Try," he says, “if you can imagine a shoe made with half the skill which appears in the skin of the foot." Some one had spoken of a structure of the human body which he would have preferred to that which it now has. "See," Galen exclaims, after pointing out the absurdity of the imaginary scheme, " see what brutishness there is in this wish. But if I were to spend more words on such cattle, reasonable men might blame me for desecrating my work, which I regard as a religious hymn in honor of the Creator."

He was

Galen was from the first highly esteemed as an anatomist. originally of Pergamus; and after receiving the instructions of many medical and philosophical professors, and especially of those of Alexandria, which was then the metropolis of the learned and scientific world, he came to Rome, where his reputation was soon so great as to excite the envy and hatred of the Roman physicians. The emperors Marcus Aurelius and Lucius Verus would have retained him near them; but he preferred pursuing his travels, directed principally by curiosity. When he died, he left behind him numerous works, all of them of great value for the light they throw on the history of anatomy and medicine; and these were for a long period the storehouse of all the most important anatomical knowledge which the world possessed. In the time of intellectual barrenness and servility, among the Arabians and the Europeans of the dark ages, the writings of Galen had almost unquestioned authority;18 and it was only by an uncommon effort of independent thinking that Abdollatif ventured to assert, that even Galen's assertions must give way to the evidence of the senses. In more modern times, when Vesalius, in the sixteenth century, accused Galen of mistakes, he drew upon himself the hostility of the whole body of physicians. Yet the mistakes were such as might have

15 Sprengel, ii. 15.

17 De Usu Part. iii. 10.

16 De Usu Part. v. 5, (on the kidneys.)

18 Sprengel, ii. 359.

been pointed out and confessed19 without acrimony, if, in times of revolution, mildness and moderation were possible; but an impatience of the superstition of tradition on the part of the innovators, and an alarm of the subversion of all recognized truths on the part of the established teachers, inflame and pervert all such discussions. Vesalius's main charge against Galen is, that his dissections were performed upon animals, and not upon the human body. Galen himself speaks of the dissection of apes as a very familiar employment, and states that he killed them by drowning. The natural difficulties which, in various ages, have prevented the unlimited prosecution of human dissection, operated strongly among the ancients, and it would have been difficult, under such circumstances, to proceed more judiciously than Galen did.

I shall now proceed to the history of the discovery of another and less obvious function, the circulation of the blood, which belongs to modern times.

CHAPTER II.

DISCOVERY OF THE CIRCULATION OF THE BLOOD.

Sect. 1.—Prelude to the Discovery.

THE blood-vessels, the veins and arteries, are as evident and peculiar in their appearance as the muscles; but their function is by no means so obvious. Hippocrates' did not discriminate Veins and Arteries; both are called by the same name (pλέßɛs); and the word from which artery comes (aprnpín) means, in his works, the windpipe. Aristotle, scanty as was his knowledge of the vessels of the body, has yet the merit of having traced the origin of all the veins to the heart. He expressly contradicts those of his predecessors who had derived the veins from the head; and refers to dissection for the proof. If the book On the Breath be genuine (which is doubted), Aristotle was aware of the distinction between veins and arteries.

2

66

Every artery,"

19 Cuv. Leçons sur l'Hist. des Sc. Nat. p. 25.

1

Sprengel, i. 383.

2 Hist. Animal. iii. 3.

5

it is there asserted, "is accompanied by a vein; the former are filled only with breath or air." But whether or no this passage be Aristotle's, he held opinions equally erroneous; as, that the windpipe conveys air into the heart.* Galen was far from having views respecting the blood-vessels, as sound as those which he entertained concerning the muscles. He held the liver to be the origin of the veins, and the heart of the arteries. He was, however, acquainted with their junetions, or anastomoses. But we find no material advance in the knowledge of this subject, till we overleap the blank of the middle ages, and reach the dawn of modern science.

6

The father of modern anatomy is held to be Mondino, who dissected and taught at Bologna in 1315. Some writers have traced in him the rudiments of the doctrine of the circulation of the blood; for he says that the heart transmits blood to the lungs. But it is allowed, that he afterwards destroys the merit of his remark, by repeating the old assertion that the left ventricle ought to contain spirit or air, which it generates from the blood.

Anatomy was cultivated with great diligence and talent in Italy by Achillini, Carpa, and Messa, and in France by Sylvius and Stephanus (Dubois and Etienne). Yet still these empty assumptions respecting the heart and blood-vessels kept their ground. Vesalius, a native of Brussels, has been termed the founder of human anatomy, and his great work De Humani Corporis Fabricâ is, even yet, a splendid monument of art, as well as science. It is said that his figures were designed by Titian; and if this be not exactly true, says Cuvier," they must, at least, be from the pencil of one of the most distinguished pupils of the great painter; for to this day, though we have more finished drawings, we have no designs that are more artistlike. Fallopius, who succeeded Vesalius at Padua, made some additions to the researches of his predecessor; but in his treatise De Principio Venarum, it is clearly seen that the circulation of the blood was unknown to him. Eustachius also, whom Cuvier groups with Vesalius and Fallopius, as the three great founders of modern anatomy, wrote a treatise on the vein azygos which is a little treatise on comparative anatomy; but the discovery of the functions of the veins came from a different quarter.

3 De Spiritu, v. 1078.

8

9

The unfortunate Servetus, who was burnt at Geneva as a heretic in 1553, is the first person who speaks distinctly of the small circulation, or that which carries the blood from the heart to the lungs, and back again to the heart. His work entitled Christianismi Restitutio was also burnt; and only two copies are known to have escaped the flames. It is in this work that he asserts the doctrine in question, as a collateral argument or illustration of his subject. "The communication between the right and left ventricle of the heart, is made," he says, "not as is commonly believed, through the partition of the heart, but by a remarkable artifice (magno artificio) the blood is carried from the right ventricle by a long circuit through the lungs; is elaborated by the lungs, made yellow, and transfused from the vena arteriosa into the arteria venosa." This truth is, however, mixed with various of the traditional fancies concerning the "vital spirit, which has its origin in the left ventricle." It may be doubted, also, how far Servetus formed his opinion upon conjecture, and on a hypothetical view of the formation of this vital spirit. And we may, perhaps, more justly ascribe the real establishment of the pulmonary circulation as an inductive truth, to Realdus Columbus, a pupil and successor of Vesalius at Padua, who published a work De Re Anatomica in 1559, in which he claims this discovery as his own.1o

Andrew Casalpinus, who has already come under our notice as one of the fathers of modern inductive science, both by his metaphysical and his physical speculations, described the pulmonary circulation still more completely in his Quæstiones Peripatetica, and even seemed to be on the eve of discovering the great circulation; for he remarked the swelling of veins below ligatures, and inferred from it a refluent motion of blood in these vessels.11 But another discovery of structure was needed, to prepare the way for this discovery of function; and this was made by Fabricius of Acquapendente, who succeeded in the grand list of great professors at Padua, and taught there for fifty years.12 Sylvius had discovered the existence of the valves of the veins; but Fabricius remarked that they are all turned towards the heart. Combining this disposition with that of the valves of the heart, and with the absence of valves in the arteries, he might have. come to the conclusion13 that the blood moves in a different direction in the arteries and in the veins, and might thus have discovered the circulation but this glory was reserved for William Harvey: so true