Book One -- The things that sustain and support the entire body, and what braces and attaches them all. [the bones and the ligaments that interconnect them]

Chapter 4 On the Structural Relationships of Bones

[Introduction to Chapter 4]
THE BONES of the human body could not be fashioned as a single continuous bone like some stone statue. Though in such a case the human fabric would be less vulnerable to injuries, and the bones would have a firmer seat and could not be dislocated, displaced, or sprained, yet because man should in no way be deprived of motion (which is thought the most characteristic feature of an animal, if anything is), and because motion would not be accomplished without the divisions and joinings of bones, it was very fitting for man to be fashioned out of many bones.

Man is made with many bones for the sake of motion
Bones were arranged next to each other not only for the sake of motion, but also for movement of a substance, for security, resistance to injury, or because the parts are different from one another. For the sake of motion the bones of the fingers are joined to each other, then the ulna and radius with the humerus, the humerus with the scapula, the femur with the tibia, and countless other such connections of bones.

For the movement of expiration
I will state that sutures of the head are formed for the passage or movement of a substance, when I explain that they transmit the sooty waste 1 of the head and provide a path for the fibers of the hard membrane of the cerebrum from which the membrane enclosing the skull [dura mater cranialis] is made.

To withstand hardship
Also in my account of the sutures of the head (to look no further for examples) 2 you will hear that the skull is formed not of one bone but many, lest if it is damaged in one part it will burst wide open, and as in an earthen jar the damage extend beyond the edge of a bone; but the breakage will come to an end with the bone, at the suture.

For the variety of the parts
Also, that bones are multiple because of the variety of the parts, you will understand in my explanation of the joints of those bones where the soft bones of the vertex [os parietale] are joined to the hard bones of the temple [os temporale]. All bones 3 are contiguous with one another, and no bone (unless perhaps the u-shaped hyoid bone is mentioned, and any that is in the base of the heart) 4 is held by itself but is either part of a continuum, or touches another bone, 5 or is bound to another; to such a degree that the sage parent of things, Nature,

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wished mankind to use the bones 6 as a single and continuous thing and also as many bones, for the uses I have recorded. 7 I think it less important that cartilage, and sometimes a portion of ligament, comes between bones that are joined, than that because of such tissue we should be able to say less precisely with Aristotle 8 that the bones are contiguous with each other. Yet at the same time he attests that the bones, like the veins, are continuous, stating in addition that they take their beginning from the spinal column in the same way as the veins begin from the heart. The Greeks named this single series of joined bones the skeleton, as if it were a dried cadaver. 9 Just as the use of the bones’ structure of joints is varied, so also is its system complex. I will now first summarize it in a table, and then explain more fully the individual types of joint.

The bones of the human body are joined to each other by structures which

All of the above are joined

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By these varieties of joints, then, the bones are connected to each other.

a)/rqron, joint. Visible motions: dia/rqrwsij
Now in the first place, there is the natural arrangement of bones for the sake of voluntary motion, called by the Greeks a)/rqrwsij and a)/rqron, by us articulation and joint. In fact, the way this motion works is not the same in all joints, since some motions are evident, and all can see them: no one fails to perceive the head being moved above the neck [articulatio atlanto-occipitalis], the femur in the hip bone, the hand on the forearm, and, in addition to countless joints, the fingers themselves [articulationes metacarpophalangeales et interphalangeales]. 16 This type of articulation, showing visible motion, is called dia/rqrwsij, as if the dearticulation were loose. Likewise Hippocrates called it a)pa/rqrwsij, so to speak an “abarticulation” 17 or loose articulation.

Obscure motions
The motion of other joints is neither vigorous nor obvious, but obscure and so difficult to perceive and hidden that individual motions cannot by any means be readily distinguished. The movement of the joint of the metacarpal and carpal bones is not obvious to anyone. But if you first stretch the fingers along a level surface and then place the little finger under the middle finger and the ring finger so as to make an X figure and attempt to form a kind of semicircle with the roots of the fingers, the metacarpal bones will not appear utterly immobile. The same thing occurs also in the joints of the carpal bones with each other, 18 of the calcaneus with the talus, of the talus with the navicular bone, and again of this with the three bones 19 [os cuneiforme mediale, intermedium, laterale] of the tarsus, of the calcaneus with the cuboid bone of the tarsus, and of the bones of the tarsus with the metatarsal bones. Unless you observed very closely, you would not notice even the most obscure motion. 20

suna/rqrwsij or coarticulation
This type of articulation is called suna/rqrwsij, what you might call “coarticulation,” being distinguished from dearticulation in the quantity of motion alone.

Not all joints move in the same way
Nature has linked each type of articulation in no simple kind of structure, as equal motion is not given to all joints. Some are flexed and extended, and adducted and abducted on this side and that, and finally they are also rotated in a circle. The femur and the arm show these motions [articulatio spheroidea]; you adduct the arm to the chest, you take it back to the dorsum, then you move it upward to the head, and downward to the hips; finally, you move it around as well when you fix your thumb to the table and make a circle as much as you can with the rest of your fingers. So also you move the femur forward and backward and inward toward the other femur, and outward away from it; likewise you turn it in a circle when you fix your heel on the ground 21 and move the toes this way and that to the sides. This is the sense in which it is convenient to understand the motion of rotation, but not when you move the arm now forward, now upward, now backward, now downward in successive motions as if in a circle [circumduction]. We shall pursue this at greater length in explaining the uses of the muscles. 22 Other joints are only bent and extended and moved to the sides, lacking all movements of rotation [ginglymus], for example the first joints of the digits, 23 and the wrist itself where it is joined to the forearm. Others are bent and extended and at the same time rotated, without at the same time claiming for themselves any motion to the sides. So the radius together with the ulna 24 are bent and extended on the humerus, and even rotated on it whether they are pronated or supinated [articulatio trochoidea]. Others are only bent and extended, like the ulna to the humerus, the tibia to the femur, the second and third joints of the fingers, and the third joint of the thumb [ginglymus]. Others are only rotated [articulatio trochoidea], as the first vertebra of the neck is rotated above the second as if on an axle with the entire head, and as the radius is moved above the ulna only in a pronating or supinating rotary motion. Since, therefore, all joints do not command the same movement, it should appear by no means strange that they are put together with a different form of construction.

Three forms of joint
The type or form we have been describing is tripartite, given three names by the oldest of the Greeks who taught their sons the method of dissection: e)na/rqrwsij, a)rqrwdi/a, and gi/gglumoj. 25 These names were perhaps confused later on by Diocles and those who first passed on in their commentaries the method of dissection.

E)na/rqrwsij: Enarthrosis 26
Enarthrosis denoted that type of articulation in which the cavity or hollow of the receiving bone is deep, carved out like a vinegar-cup or acetabulum. The swelling head that articulates with it, as well as the hollow itself, are simple in this variety of articulation: a single hollow and a single head, just as we see occurs in the articulation of the femur with the hip [articulatio iliofemoralis], the humerus with the scapula [articulatio glenohumeralis], and the metacarpal and metatarsal bones with the first bones of the digits [ossa digitorum]. These joints are given many visible motions. The femur and the arm bone, 27 which we call the humerus, are flexed, extended, moved sideways, and rotated. The first bones of the digits [phalanx proximalis] are not rotated, 28 which you will hear happens not only because of the arrangement of the muscles and sesamoid bones but also because of the construction of the joint [ginglymus]. The carpus is joined to the radius by this kind of joint: it is flexed, extended, and moved sideways. The radius is joined to the humerus [articulatio humeroradialis] by enarthrosis, because of which it is capable of even more movements; it is flexed and extended together with the ulna, and then rotated [articulatio trochoidea], so that it is agreed that in simple joints which are constructed with a continuous and uninterrupted coating (so to speak) of cartilage, Nature devised enarthrosis whenever it seemed best to her that the bone be moved with many motions,

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using in those motions the simplest possible and least complex connection of the bones. To such a bone, the navicular, a head [caput tali] (join O in figure 3 Chapter 33 to k of figure 11) is joined by this type of articulation. 29 When we discuss them, we shall also show that certain carpal bones (figure 2 Chapter 25, joint of no. 7 to 1) are joined by this means; similarly, the cartilages of the second, third, fourth, and fifth ribs are joined to the sternum by this type of articulation [articulatio plana]. For the time being it is enough to explain the varieties of joints and their character, and to consider in them the intention of the Maker, adding only such examples as these latter ones to be counted among those having obscure motions. For to enumerate all the joints every time, easy as it would be for me to do, would encumber the beginner in anatomy with bones not yet explained, and the difficulty of the task would deter him from the fairest investigation of the works of God.

A)rqrwdi/a is a type of joint with a lightly and superficially hollowed depression and a low head, as if it were made by the attachment of flat surfaces. 30 And whereas in enarthrosis it is easy to tell which is the head and which the depression, in arthrodia both are so obscure that you do not know to which bone you should ascribe the depression or the head, just as if you were to imagine two flat surfaces pressing into each other. By this type [articulatio plana] the three inner bones [os cuneiforme mediale, intermedium, laterale] of the tarsus are joined to the navicular bone, the metatarsal bones to those of the tarsus, some carpal bones to metacarpals, the fourth bone of the carpus [os pisiforme], which will be called the upright bone, 31 to the third carpal bone [os triquetrum], and the clavicle to the acromion [articulatio acromio-clavicularis]. 32 In these joints the motions are so obscure that they may be perceived only with great difficulty.

When Nature formed arthrodia 33
It is as if Nature employed this type of articulation in a simple joint where she decided the bone would move scarcely a little bit; for you will nowhere find a simple and authentic arthrodia where motion is obvious. Likewise you may observe a double arthrodia capable of obvious motion, but it will be a virtually single and simple motion. The first vertebra [atlas] of the neck will be proven to make no other movement than a clear rotation [articulatio trochoidea] over the second [axis], and at the same time the first vertebra of man is joined to the second at two points (join Y in fig. 4 ch. 15 with c in fig. 5; then a, b in fig. 4 with d, e, f, in fig. 5; finally L in fig. 4 with g in fig. 5) [articulatio atlanto-axialis mediana et lateralis] by arthrodia: on each of the sides of the dens of the second vertebra, 34 and the dens itself is in a fashion connected [ligamenta alaria] to the first vertebra by a kind of arthrodia. 35 Yet in these vertebral connections, the hollows [facies intervertebrales] and the heads are still more obvious than in the simple arthrodiae that we mentioned before. In addition, you will observe this kind of arthrodia in the remaining vertebrae of the neck and all the vertebrae of the thorax (join X and Y [fovea costalis superior] in figure 3, Chapter 16 with a and b [fovea costalis inferior] of figure 2 or c of figure 3) as far as the one that I shall explain is received by the vertebrae above and below it. 36 The connections of these vertebrae [articulationes zygapophysiales], which are located near the root of the spine or lower process of the vertebrae, are so joined together that the portions of one vertebra that enter another swell out very gently, and the parts admitting the other vertebra are hollowed only on the surface. But in these vertebrae some motion to the sides 37 is observed besides the flexion and extension. Thus if we have said that this kind of double articulation of the vertebrae with each other is arthrodia, we will admit that it is not always made for the sake of a completely simple motion.

Ginglymus 38
Gi/gglumoj, considered the third species of joint, is made with obvious hollows and heads, but by no means simple ones. Ginglymus occurs whenever bones are joined by entry into each other, so that the protuberant end of one bone nests into the concave end of another and the hollow of one bone admits the protuberant part of another, just as if you joined the fingers by pressing them into each other, or if you compared this species of joint with the hinges of doors in which the iron driven into the wall receives that which is attached to the door, and the iron from the wall enters up into that of the door [articulatio trochoidea]. The present species of articulation got its name from this model. 39

Here A marks the iron or pivot driven into the wall, B the iron that is attached to a door or window.

This occurs in the knee (compare G, F, I in fig. 7, ch. 31 with E, F, I in fig. 1, ch. 30): the tibia has two hollows [condylus medialis et lateralis], between which a tubercle protrudes. The lower part of the femur puts out two heads [condylus medialis et lateralis] that enter the hollows of the tibia; in between the heads a hollow [fossa intercondylaris] is seen that receives the tubercle [eminentia intercondylaris] of the tibia (in Chapter 27 figure 2, join G, H, I to I, K, M). The same system [ginglymus] is preserved in the second and third joints of the four digits of the hand and foot, in the third joint of the thumb, and the second of the big toe: the upper [proximal] bone of these joints has heads in the middle of which there is a depression, while the lower [distal] bone, closer (so the speak) to the nail, contains two depressions separated by a tuberosity. Moreover, the joint of the humerus with the ulna is quite elegantly made with a ginglymus: the depression [incisura trochlearis] of the ulna receives the tubercules [trochlea humeri] of the humerus, and again the protrusions [olecranon] [processus coronoideus] of the ulna marvelously enter the depressions [fossae olecrani, coronoidea] of the humerus.

When Nature formed ginglymus
In these bones the ginglymus is made in one continuous joint which has the capacity only for extension and flexion and no other motion, just as if the Maker of things had thought this form of joint should be used as often as it was proper for a joint only to be flexed and extended, or moved only with another simple motion. In this category also (so far as I can conjecture) the ancient Greeks placed bones joined by distinct and separate articulations that are responsible for a simple motion, especially when such articulations vary in what they are joining.

In what ways double joints are formed
The radius (figure 1, chapter 24; or join m in figure 3 to l in figure 5, and p in figure 5 to o in figure 7) is joined to the ulna by a double joint [articulatio radio-ulnaris proximalis et distalis], by virtue of which it is capable only of a simple motion, which is into a prone or supine position. Near the humerus, the ulna admits the capitulum of the radius into a depression [incisura radialis] carved into it, and next to the carpus the hollow [incisura ulnaris] of the radius receives the capitulum of the ulna.

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The same thing is seen in the joint of the calcaneus and the talus [articulatio subtalaris] (if I may for a moment consider ginglymi producing an obscure movement) [facies articularis calcanea posterior]. In its posterior area the talus receives a projection (insert P of fig. 7, ch. 33 into Q of fig. 4 and S of fig. 4 into R of fig. 7) [facies articularis talaris posterior] of the calcaneus, and in the anterior depression [facies articularis talaris anterior et media] of the calcaneus the head of the talus is connected by a joint [articulatio talocalcaneonavicularis], so that with the best justification the bones are said to be articulated here also by mutual entry. The ancients seem also to have placed double articulations in this category, even though they are not made by a mutual entry of different types, but when bones join is a similar manner on both sides, as the connection [articulatio atlanto-occipitalis] of the head to the first vertebra may be judged. For where the two depressions (join B in fig. 1, ch. 15 to N in fig. 2 and D, E, F, G in fig 1 to O, P, Q, R in fig. 2) [facies articularis superior] of the first vertebra are separated from each other, the two heads [condylus occipitalis] of the occipital bone are articulated as if by enarthrosis, and the articulation of the right side differs not at all in type or form from that of the left. The other vertebrae are joined in the same way. The inferior or lower one is connected to the one above by a double joint [articulationes zygapophysiales]; these are the joints which we shall say are at the base of the spine or posterior process of the vertebrae. I am not speaking now of the connection [discus intervertebralis] of vertebrae which they form on their own bodies (R in the figure in Chapter 14), since this varies as far as the present subject is concerned. Thus, as far as the form of articulation is concerned, the vertebrae located above the twelfth vertebra of the thorax are joined together in the posterior joints by arthrodia; but those that lie below the twelfth are joined by a kind of enarthrosis (join O in fig. 2, ch. 14 to K, L, M in fig. 3). But if we include this kind of vertebral joint as ginglymus because they are double (one to each side), we would also admit that certain articulations of this kind [articulatio plana] have not just a simple motion, since besides flexion and extension the vertebrae are moved a little to the sides as well. Yet I do not believe the leading ancient anatomists said the vertebrae were articulated by ginglymus because (with the sole exception of the first cervical and generally the twelfth thoracic) one vertebra is always received in its upper portion by another, and in its lower portion receives the vertebra below; or, on the contrary, that it receives another with its upper portion, and its lower is received. But this is what Galen affirms, 40 saying that ginglymus is made in this way, and perhaps not noticing that if what he claimed were so, three bones would have to meet at the articulation: the first bone would be a vertebra that is received on its upper side, the second a vertebra which receives this upper side, and the third a vertebra which is received by the lower side of the middle or first vertebra (see the three vertebrae, fig. 3, Chapter 19). For one and the same vertebra to receive and be received, it would be necessary to have in addition to that vertebra both a receiving vertebra and one that is received converge upon it. And by this reasoning, ginglymus would have to be applied to a great number of bones: 41 to those which enter another bone with their lower portion, and admit another with their upper; or contrarily, which on their superior surface enter one bone, and receive another on their lower, without respect to the form of articulation. The first bones of the digits (B in fig. 1, ch. 27 and E in fig. 2) would be considered to be of this type; they are joined on their superior surface by enarthrosis to the metacarpal bones, and in their lower portion they enter the hollows of the next digital bone. I shall deal at length in the appropriate place with the joints of the digits and vertebrae; now I shall explain joints showing no motion at all [synarthroses], noting first that no connection of bones so far mentioned is made without the hollows and heads or surfaces being covered by a smooth and slippery cartilage [cartilago articularis], the only exceptions being the connection of vertebral bodies (R in the fig. for ch. 14) to each other and that of the sacrum with the two bones [ossa ilii] joined to it [articulatio sacroiliaca], where you will later hear that cartilaginous ligament 42 intervenes specially. The joints that will now be described, deprived of all motion whatsoever, are never made with a smooth, slippery contact.

The first of these is called gomphosis, and it occurs when bone is fixed in bone like a nail. By it, every tooth (insert the set of teeth marked A, A in the figure for ch. 11 into fig. 4, ch. 6) is driven into the sockets [alveoli dentis] in the maxillae [maxilla et mandibula] so much like a nail that it cannot be moved even the slightest bit. The ancients sometimes compared a nail-like connection also to a joint, but for another reason, when they stated that bones are fitted together for the benefit of another bone as if by the intervention of a kind of nail — as Aristotle affirms when he writes that two hollow bones have a nail (clavus) between them, believing that the tibia and the calcaneus have a cavity [sulcus] (consider how in the three skeletons W is between F and a; or compare the figs. of ch. 31 with those of ch. 33), and that the talus enters those cavities [facies articularis inferior] with its own protrusions [trochlea tali] like a nail, as if two posts were fastened with the same spike. 43 In Chapter 33 the nature of the talus will be explained; its connection [articulatio talocruralis] to the tibia and the calcaneus is articulated by ginglymus in both men and quadrupeds. For humans are not without a talus, though it differs in shape (but not location) from that of single-hoofed and cloven-footed animals. 44 For in all it lies beneath the tibia and is articulated to the calcaneus, or what takes the place of a calcaneus. The femoral bone, as much in birds as in horses, pigs, and other quadrupeds, deceived Aristotle and Galen in the third book of De usu partium, 45 because in those the femur is not as easy to see as in humans; as I shall say in the appropriate place, Aristotle in his book De communi gressu animalium [De incessu animalium] 46 wrongly handed these things on to posterity because the femur and humerus in quadrupeds and birds was unknown to him.

afh/: Suture
The suture which the Greeks call rhaphe is a kind of joint that resembles things sewn together. Many, when trying to explain this, define it as a serrated seam [sutura serrata] and structure, others as an exact fingernail-tight union. The former remind us of the fitting together of two saws facing each other, where the projecting portions of each saw enter the open spaces of the other. The latter are said to be fitted “to a fingernail” when the projecting parts

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built in the shape of fingernails are inserted into depressions in which they can fit perfectly [sutura dentata]; this is the series of joints with which we often see the boards of chests or litters put together. 47 The later examples explain the shape of a suture more accurately than the earlier ones. So those find the best approximation who compare sutures to the appearance of ornamental borders of a seam when, as we said about fingernails, flowerets in one piece of cloth are sewn into the openings of another with matching inlets. The bones of the head are mostly joined by sutures of this type [suturae cranii]; and among the others, that suture most elegantly shows its type which we compare to the letter L [sutura lambdoidea] in the occiput (figure 1, Chapter 6, and A, B, C, D in figure 3, Chapter 6).

[Four illustrations showing types of suture at left margin of page:] (1) serrated fastening [sutura serrata]; (2) fingernail-like-like seam [sutura dentata]; (3) attachment of boards (rabbet joint); (4) fancy border seam. 48

Next, a a(rmoni/a is a structure of bones along a simple line, joined without any fitting together of swellings, depressions, or roughness. Certain bones of the upper maxilla, and especially the bones of the nose, are thought to be joined in this fashion. Such a joint is hardly ever made exactly like a simple line [sutura plana]: numerous rough places that fit into each other in a continual series occur in harmonia when the bones are broken; for this reason the ancients seem generally to have included harmoniae under the term “sutures.”

Su/mfusij is the natural union of bones, a form of attachment by which epiphyses are joined to their bones: in younger persons (1, 2, 4, 5 of the figure in ch. 40, Bk. 2), when the bones are still soft and spongy, by the intervention of cartilage [cartilago fibrosa]. In those that are older, when the bones have hardened, the epiphyses are so integrated with the bones without intervening substance that you can hardly make out the line of juncture. By this union also the bones joined to the sides of the sacrum come together in the pubis [symphysis pubica] (j in the first skeleton). In quite young children, the bone [os coxae] on each side is seen to be made out of three bones [os ilii, os ischii, os pubis]; these are distinguished by three lines [epiphyses] that meet in the acetabulum of the hip bone. It can also be seen in lambs, where cartilage [hyaline] is in these lines, as in children. In slightly older persons, those three pieces have so fused that no kind of line presents itself. These bones will be described in the appropriate chapter. Similar observations will be made in the chapter on the vertebrae, which in children are also composed of several parts; likewise the occipital bone and many others of the body, which are named as a single bone because the appearance of a joint [synchondrosis] is completely hidden in older persons. The author of the Introductory Book or The Physician, which is ascribed to Galen, does not, in introducing the study of the bones, call the union we have just described a symphysis; he applies the term instead to sutures that more or less resemble harmoniae. He calls the unions of the bones of the upper maxilla symphysis (although not rightly). 49

Substances that aid the union of bones: Ligaments
Every type of union of bones is made with the aid of some part, or of no part. For all joints (see fig. in ch. 1, Bk. 2) are bound together by ligaments, which clothe the bones on all sides. Sometimes these actually come between the bones, as in the joint of the femur with the hip [ligamentum capitis femoris] and in joining the bodies of the vertebrae [discus intervertebralis]. This connection of bones with the aid of ligaments is called by the Greeks sunneu/rwsij, 50 derived from “nerve,” a word applied to what are properly called ligaments and tendons, as well as those that come out of the cerebrum and dorsal medulla. The ancients, like laymen today, understood all of these as “nerves”; and Aristotle especially does so at all times, particularly when he describes the attachment of the bones. 51

Flesh: syssarcosis
Some bones are joined also by the aid of flesh, as in general all joints overlaid by muscles (passim in the tables of muscles, e.g., Q, X in the 7th). For when muscles originating from one bone or other body 52 are inserted in another, they are rightly considered to act as bindings, and they bind the bones together. Moreover, because muscles are called “flesh” by most of the ancients, especially Aristotle, a connection made by muscles is deservedly called sunsa/rkwsij. 53 The teeth as well seem to be held in their alveoli by a kind of flesh [periodontium] so that by this reckoning, so to speak, a construction of the bones is found in which flesh [fascia] not only surrounds a joint on the outside in the manner of muscles, but it intervenes in the joint as well.

Cartilage: synchondrosis
In addition, other bones are joined by the medium of cartilage: epiphyses (Book 2, Ch. 40, nos. 1, 2, 4, 5) in very early life are attached to their bones by means of cartilage, as are the bones of the pubis [symphysis] (j in the first skeleton) and the ossicles of the hyoid bone (G in figs. 1, 2, ch. 13). 54 This type of connection from cartilage is called sugxo/ndrwsij.

Bones that are joined with the aid of no substance
Sutures and harmoniae, however, come together with the aid of no substance other than the structure of the bones. For although the fibers of hard membrane [dura mater encephali] investing the cerebrum cross some sutures, they do not thereby bind them together, just as the cartilages [cartilago articularis] covering bones in joints contribute nothing to the strength of the bones or their connection. Also in older persons, epiphyses are no longer attached to bones with the aid of cartilage acting as glue, but the cartilage is completely gone and they are so attached that, as I previously observed, it is difficult to see the place where they are joined.

Some major disagreements in this chapter with the opinions of Galen 55
I had intended to put an end to this chapter and direct my account to descriptions of individual bones, had not the authority of Galen greatly delayed me; but it justly prevents me from so lightly passing by matters which in the present chapter diverge from his opinions. From many opinions besides those already mentioned, I would cite something, first in his book De ossibus, where he straightforwardly (and with no modest self-praise

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in the first Book of De administrandis sectionibus) enumerates the structures of bones: 56 I have not agreed with his doctrine in which he teaches that suture, harmonia, and gomphosis are types of synarthrosis. 57 For I have ascribed to synarthrosis an obscure and not obvious movement, and I have stated that synarthrosis and diarthrosis are made by the same varieties and forms of articulation. I have given suture, harmonia, and gomphosis not an obscure and difficult motion, but no motion whatever, and I have by no means included these types of connection, with Galen, in the category of joints. He would assuredly not have done so, unless in explaining severally the construction of the carpal, metacarpal, tarsal, and metatarsal bones, and the costal cartilages with the sternum, he had wished to state falsely 58 that these are joined by synarthrosis. For when he was saying correctly 59 that these bones are attached by synarthrosis, should he not have noticed that they are not connected by suture, harmonia, or gomphosis? This certainly would have been the case if he had been correct in determining that harmonia, suture, and gomphosis are types of synarthrosis. But as I see it, it will be a simple matter for anyone to make up his own mind about synarthrosis, as long as he bears in mind that it is construed quite differently in almost all the books of Galen than it is in the beginning of his book De ossibus. Even in Chapters 13, 19, 21, and 24 of the same book, Galen feels differently than at the beginning. Moreover, the author of Introductorius seu Medicus, not accepting the opinion of Galen and dividing the connections of bones in his own way, says: “The bones are put together either for motion, and this type of construction is called arthron or joint; or for no motion, and they are called synarthrosis.” He lists their types as suture, gomphosis, and symphysis. 60 But by this account synarthrosis cannot in any way be accommodated to the makeup of the carpal, metacarpal, tarsal, and metatarsal bones, since they are connected to each other by neither suture nor gomphosis, and much less by symphysis.
I have also departed further from Galen’s opinion in saying that all attachments of bones are either aided by some substance, 61 or by none; Galen attributed this only to symphysis in De ossibus, and he counted synneurosis, syssarcosis, and synchondrosis only as types of symphysis. 62 His own account gave me the first reason for not following him, where he taught that soft, spongy bones [ossea spongiosa] are attached to each other by symphysis with nothing in between, but drier and denser bones [ossea compacta] come together by means of intermediate materials. 63 For I learn that in bones which are still soft and tender, epiphyses are united to their bones by cartilage [cartilago epiphysialis], while in hard, dry bones and bones of old people, nothing at all assists symphysis. Moreover, I can find absolutely no symphysis or union that one could truly say was made with the aid of a ligament; synneurosis could not therefore be included under symphysis, bearing in mind that no union [symphysis] is completed by aid of a ligament in the way that articulations all certainly come together with the aid of a ligament, in some cases (as I have said before) wrapped around the joint, in others coming between the two bones where they meet [articulationes synoviales]. As I considered each case exactly, I found still less symphysis where one would rightly say the attachment was made by flesh. For in no connection of bones does flesh [textus connectivus] play a role unless perhaps in the connection [periodontium] of teeth with the maxillae, which is judged to be gomphosis, not symphysis; and however immobile the teeth, they are not more so than in harmonia or suture. But on the other hand almost all articulations are held together with the help of flesh, i.e., of muscles. We have said that this bond was called syssarcosis 64 by the ancients. No one could say this is a species of symphysis.
In addition to this (so that an end may finally be put on this chapter), a passage in the second book of Aristotle’s De partibus animalium has warned us the more quickly to disagree with Galen, where Aristotle affirms that the bones are joined by nerves, 65 flesh, and cartilage, very learnedly assigning this connection categorically to all meetings of bones. 66 Yet Galen knowingly passes over this very opinion of Aristotle when, forgetful of the things he taught in his book De ossibus, he runs through the structure of bones in a perfunctory though quite elegant way at the end of the second Book of De administrandis sectionibus, more or less summarizing the words of Aristotle. 67

Appendix: Ginglymus (the hinge joint, 1555 version)
Gi/gglumoj is made with obvious depressions and heads, but they are in no way simple, nor do they consist of a single convex, concave, or flat surface. Ginglymus occurs when bones are joined by entry into each other in such a way that the prominences of one bone enter depressions of the other, 68 and the depressions of one bone in turn admit the prominences of the other, just as the hinges of doors and windows, from which this third type of joint takes its name, are built. Just as two principal types of hinge are seen, so there is above all a double system for the mutual attachment of bones. Hinges, //1555 p. 17// which generally have two connected beams, are protuberant and hollow in such a way that the protruding parts of one iron piece are received by the hollow parts of the other and the hollow parts of one admit the protruding parts of the other, and the pin then runs through all the cavities at once. 69 The hinges by which doors and windows are attached to walls are so arranged that the iron piece attached to the right wall has a smoothly rounded protrusion running perpendicularly upward which fits up into the hollow circle of the iron piece attached by nails to the door or window, so that the hollow circle, ring, or vertebra 70 receives the rounded protuberance, and the iron piece from which the latter is produced takes on the vertebra by mutual entry. 71 In the likeness of these hinges (particularly if one member has just one protrusion [eminentia] in its middle and is cut away above and below, while the other shows two protrusions and is hollowed out [fossa] between them) the second and third joints of the digits of the hand and foot are joined and, in addition to very many others, the joint [articulatio tibiofibularis] of the femur to the tibia. In these joints, one bone has two heads separated by a depression between [fossa intercondylaris]; the other has two depressions [condylus medialis, c. lateralis] set off by a prominence [tuberculum intercondylare] between. In this way the two heads of one bone enter the twin depressions of the other, and the depression of one bone receives the protuberance of the other. The ulna is seen to be joined to the humerus in the manner of the second hinge, when the round depression [incisura trochlearis] of the ulna is flexed and extended on the orbit or wheel of the humerus [trochlea humeri], or otherwise swiveled upon it — though in this joint too [articulatio humero-ulnaris] many features besides resemble the first hinge. Nature contrives such joints when she particularly wishes to promote the interests of their strength and it suffices that they perform only a single motion, as the joints just mentioned attest, which we can only flex and extend, as they require no other motion.

The upper figure illustrates a hinge by which we write here that two beams join. A marks one iron, B the other; by means of the pin, marked C, they are secured to their point of mutual entry. In the lower figure another hinge is drawn in which D identifies the iron attached to the wall, E the iron by which it is attacked to the door or window by nails.

Why Nature sometimes joined two bones with several joints
It is fitting to understand the purposes of Nature so far mentioned in forming three types of joint in cases where they are simple and single in the attachment of only two bones. For on occasion when constrained by an unusual situation, she was unable to join two bones with a simple joint, but fashioned two and sometimes more connections or joints at a distance from each other and not immediately contiguous. To prevent the radius from separating too far from the ulna midway along the forearm without good cause, she joined the radius to the ulna by a double joint 72 rather than a simple tight joint through the entire length of the forearm: next to the bend of the elbow, where the capitulum of the radius goes up into the depression of the ulna and next to the brachium, where the capitulum of the ulna articulates into the depression of the radius, though at those two joints the radius only rotates or is pronated and supinated. Next, because of the passage of the dorsal medulla [medulla spinalis], the occipital bone is connected by a double joint [articulatio atlanto-occipitalis] to the first vertebra, each constructed more or less in the style of enarthrosis; but by virtue of that joint, the head moves only backward and forward above the first vertebra, rightly because of the structural principle in joints separated from each other. In addition, the first vertebra is joined above the sides of the second vertebral body by two joints resembling arthrodia or flat joints; and the dens of the second vertebra is joined to the first by a kind of enarthrosis. 73 Yet in those three joints the first vertebra and the head is only rotated above the second [articulatio trochoidea] (contrary to what Galen believed, as we shall later explain). Moreover, because also for the sake of the dorsal medulla the other vertebrae of the dorsum had to be perforated and at the same time made in a complex way, Nature employed no simple connections and joints in the juxtaposition of // 1555 p. 18 // two vertebrae. In addition to a rare and peculiar articulation by which the vertebral bodies are attached by no smooth and slippery point of contact, as are all the other joints, there is a kind of arthrodia [articulationes zygapophysiales] from the second cervical vertebra to the twelfth thoracic by which the processes of each lower veretebra that we will call the ascending are placed beneath the descending processes of the incumbent vertebra placed above it. At the same time, these vertebrae experience lateral motion in addition to their obvious flexion and extension; similarly the lumbar vertebrae, which like the twelfth thoracic are articulated by enarthrosis of the descending processes into the ascending processes of the vertebra beneath. I do not know what came into Galen’s head when he classified vertebral articulation as ginglymus. 74 For though besides the first cervical and the twelfth thoracic (the latter of which is received above and below via its own ascending and descending processes by the vertebrae next to it, like the first, as if admitting the bones coterminous to it above and below) all the vertebrae are on one side received and on the other, as I have said, receive; nevertheless this must not be classified ginglymus, as he thought. For Galen did not consider that he had assigned to ginglymus three bones, as follows: the first, one which is received on its upper surface; the second, one that admits this upper surface; and the third, one that is received by the lower surface of the first bone. But now it would be timely to go into joints which are lacking in any motion, of which the first is called gomphosis. 75

Book One -- The things that sustain and support the entire body, and what braces and attaches them all. [the bones and the ligaments that interconnect them]