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 21 On the Scapuli

[Figures and figure legend]

The next page shows the index of the three figures which are set forth here, and their characters.

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The first figure of the twenty-first chapter illustrates the inner or anterior surface [facies costalis] of the right scapula, which rests upon the ribs. 1 The second shows the outer or posterior surface [facies dorsalis] of the right scapula. The third has the scapula of the right side shown sidewise [margo medialis], so as to display the hollow [fossa supraspinata] of the convex, exterior surface of the scapula which lies between the upper side 2 of the scapula and the spine of the scapula [spina scapulae]. This will presently be made clearer by the figure legends. 3
In the first figure, Z [angulus superior], X [margo medialis (epiphysis)], and Y [angulus inferior (epiphysis)] mark the base of the scapula, the scapula being more or less triangular. Z, a, and A mark the scapula’s upper side, and Y and B the lower side 4 of the scapula, so that Z [angulus superior] is the upper angle of the base and Y [angulus inferior (epiphysis)] the lower. A and B [cavitas glenoidalis] are the third angle of the scapula, which the upper and lower sides of the scapula form. These letters mark those items incidentally; each letter signifies a feature distinct from the others in the following way.
A, B 1 , 2 Depression [cavitas glenoidalis] of the scapula into which the head of the humerus [caput humeri] is articulated. 5 In the second figure, the lower portion of the depression, which is more or less round, is marked B. A is the narrower upper part, and the contracted A in the first figure illustrates the protruding part [tuberculum supraglenoidale] of the depression or neck of the scapula [collum scapulae] from which two ligaments [ll. glenohumeralia et l. coracohumerale] peculiar to this joint originate together with the outer head of the anterior of the muscles [m. bicipitis brachii, caput longum] that flex the forearm.
C, D 1 , 2 Cervix or neck of the scapula [collum scapulae]. 6 C also marks the root of the scapula’s interior process [processus coracoideus], marked E, f, and F. C in the first figure also marks a certain depression 7 visible beneath the inner process of the scapula.
E, f and F[ 1 , 2 ] in the first figure, and E and F in the second, mark the inner process [processus coracoideus] of the scapula, where F designates the protuberant part to which the clavicle is attached and by which it is all but supported. 8 E shows the epiphysis of this process, and f the rough area from which the ligament [l. coraco-acromiale] originates that extends from here to the acromion 9 (which will be marked K).
G, H 2 Root of the spine of the scapula, or the actual spine of the scapula, which in man puts forth the acromion, marked K, in the first, second, and third figures and L in the first and third. 10 Thus the longitude of the spine’s source is G and H. What runs from H to K is the acromion. Where H is seen is the point where we shall say the spine leaves the back of the scapula. The epiphysis of the acromion is separately marked K.
L 1 , 3 Depression [facies articularis acromii] quite lightly carved in the acromion, prepared for the admission of the clavicle.
I 2 , 3 Thicker part 11 of the spine of the scapula, sometimes with an epiphysis. 12 Around G, I, and H, the spine of the scapula is thicker than elsewhere. From G through I to K the rough part of the spine and the acromion is labeled. What lies between I and H in the second figure and in the first between L and a is smooth and not at all rough.
M, M, etc. 1 Tubercles resembling oblique lines, 13 forming depressions that look as if they had been impressed in the hollow of the scapula by the curvature of the ribs.
N, O 1 Hollower areas [fossa subscapularis] in the inner region of the scapula, corresponding to the letters G and H in the second figure.
P 1 Protruding, thicker portion of the lower side, 14 which bulges into the inner surface of the scapula.
p 1 Here 15 the lower edge or side of the scapula is made sharper and thereby protrudes further, so that the third of the muscles [m. subscapularis] that move the arm may more readily originate from here.
Q 1 Rough depression [margo lateralis] of the scapula’s lower side, from whence originates the inner muscle [m. triceps brachii, caput longum] of those that extend the forearm. R was accidentally left out.
S 2 Protruding part [tuberculum infraglenoidale] of the lower side near the outer surface of the scapula.
T 2 Depressed, wide area of the lower side, from which originates the third of the muscles [m. teres major] that move the arm.
V, V 2 Here the outer surface [fossa infraspinata] of the scapula is particularly concave because of the thickness of the lower side. 16 What lies between V, V and G, H is very thin and extremely fine and solid.
X 1 , 2 , 3 Epiphysis [margo medialis] of the base of the scapula, fused to the beginning of the spine itself.
Y 1 , 2 , 3 Epiphysis of the lower angle [angulus inferior] of the base of the scapula.
F 1 Portion of the upper angle that protrudes slightly into the inner region of the scapula.
Z 1 , 2 , 3 As previously stated, this marks the upper angle [angulus superior] of the base.
a 1 , 3 Semicircular foramen or depression [incisura scapulae] visible in the upper side of the scapula.
b, c 3 Area [fossa supraspinata] in the outer region of the scapula between the spine and the higher side of the scapula. Here b marks an extremely thin, slender, and somewhat transparent portion of the scapula, while c identifies the small foramen that often appears here, providing a path for the small vein to nourish the scapula at this point.

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In this figure we have illustrated the outer or posterior surface of a dog’s scapula so that the difference in the acromion or upper process of the scapula between the human scapula and that of a dog or sheep may readily be considered. A and B will therefore signify the convexity or dorsum of the scapula, A its lower area [fossa infraspinata] and B its upper [fossa supraspinata], closer to the animal’s neck or head. C and D will identify the spine of the scapula [spina scapulae], which does not extend above the neck of the scapula. E marks the scapular neck [collum scapulae].

Position and attachments of the scapula
The scapulae, one on each side (R in the three skeletal figs.), rest upon the posterior region of the thorax near the top; they are attached to the occipital bone, the cervical and thoracic vertebrae, the ribs, and the hyoid bone by muscles alone. The scapula is attached to the occipital bone with the help of the second of the muscles that move the scapula (G, D in the 9th table of muscles), 17 which also joins it to the spines of several vertebrae, 18 as does the third agent of scapular motions [m. levator scapulae] (G in the 12th table of muscles), which binds it to the neck vertebrae 19 [vertebrae cervicales]. The fourth of the muscles that move the scapula [m. rhomboideus major] (G in the 10th table) braces it on several spines of the thoracic and cervical vertebrae. The first of the muscles that move the scapula [m. pectoralis minor] (G in the 5th table) and the second of the muscles that move the thorax [m. serratus anterior] (L in the 7th table) join the scapula to the ribs. The scapula is linked to the hyoid bone by the seventh [m. omohyoideus] of that bone’s particular muscles. In humans, monkeys, squirrels, and whatever other animals have clavicles, the scapula is articulated with the clavicles (Q to l in the complete skeletons) by a mass of ligaments [l. acromioclaviculare, l. coracoclaviculare] and is conterminous with the clavicle.

Use of the scapula 20
In all animals the arm bone or humerus is articulated to the scapula (S to R of the skeletons); if you imagined a human without scapulae, you could in no way describe the shoulder joint. It is essential to the construction of this joint that the head of the humerus go into the socket of some other bone: and for it to be mobile, that it be braced in another bone as in a kind of base. 21 For the sake of such a socket, a neck protrudes — the cervix of the scapula [collum scapulae] (C, D in figs. 1 and 2) — in the end of which a socket is carved as wide and deep as is useful to the shoulder joint for various quite different motions. This is judged to be without doubt the first and foremost use of the scapulae; another immediately follows, itself not a regrettable one, to wit the fortification and protection of the parts of the thorax covered by the ribs. We watch out for the anterior parts of the thorax and forsee well ahead of time things that are about to strike and wound it, jumping aside in anticipation to avoid what is coming at us, putting up something to shield the chest, or picking up something in our hands with which to defend ourselves. Indeed, we often risk even our bare hands, judging it better that these should be hurt, fractured, crushed, or cut off than allow what could damage the chest to reach it. For the thorax is the organ of respiration, as the lung is also surrounded by it; moreover, the heart is considered the nurturer of innate heat and the seat of an irascible nature, therefore also requiring sturdier defenses. Since the same danger of blows threatens the back of the thorax as the front, but there is not the same foreknowledge of things which can harm it from the rear as in front, there being no eyes in the posterior region, it was quite fitting that Nature fashion some artifice here too and not neglect the posterior surface of the thorax. Whence, as a kind of wall and marvellous rampart she fitted there the vertebrae of the thorax, and she threw up the scapulae like two shields, bucklers, or mighty battlements. She was not unaware that from this yet another use would accrue to man, by which several muscles 22 controlling motions of the arm acquire a place of support where they may best take their origin. Surely it is a work of supreme justice that the same bone is used for such various and quite necessary functions, and that the scapulae are everywhere so formed that they could be thought made exclusively for each of these employments. 23

The triangular shape of the scapula
The scapula is quite irregular, and is different in every part. Not counting its various processes, depressions, protrusions, epiphyses, and other such features from which we have picked out the distinguishing characteristics of bones, the scapula looks more or less like a triangle formed by its several sides.

The base of the scapula
Its first side (from Z through X to Y in figs. 1-3), 24 which we shall invariably call the base [margo medialis] of the scapula, is that area which extends along the longitude of the back closest to the spines of the thoracic vertebrae. This base consists of a slanting line which is inclined above and below obliquely toward the side of the body as if in a convex arc, but in the middle is often somewhat lunate and hollow. Sometimes the whole base of the scapula

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is convex over its entire course 25 like this: ( , and this base is rather thin, though it appears somewhat thicker in its lower and upper portion than elsewhere, and the thickness of the lower part exceeds that of the upper.

Epiphyses of the base
To this base two epiphyses (one is Y, the other X in figs. 1-3) are generally attached. One, which is larger, thicker, and longer, and always appears, is located at the lower angle [Y] of the basis: it is markedly blunt, and more or less rounded. The other epiphysis [X] is some distance beneath the upper angle [Z], and fuses to that point the base from which you will hear the spine of the scapula (G, H in fig. 2, G in fig. 3) takes its beginning.

Cartilage of the base
Besides these epiphyses, there is also attached to the base a certain soft cartilage [c. hyalina] of the type by which ends of bones that are unattached to another bone are accustomed to grow. In humans, however, this cartilage is much shorter and smaller than in sheep, cattle, and other animals 26 whose scapulae lie more upon the sides of the thorax than, as in man, on the posterior of the thorax next to the vertebrae. This is how the first side or base of the scapula is arranged; the two remaining sides are different from each other.

Differences between the upper and lower sides
The lower side [margo lateralis] (from B to Y in figs. 1 and 2) runs from the lower part of the base quite obliquely upward toward the anterior. The upper [margo superior] (from Z through F to A in figs. 1 and 2) (which is as much shorter than the lower as the lower is shorter than the base itself) 27 runs somewhat downward to the exterior, proceeding more or less transversely. 28 These two sides come together at an angle (between A and B in figs. 1 and 2) and bracket at their end a rather broad part of the scapula where the cervix of the scapula is seen and the depression [cavitas glenoidalis] that receives the head of the humerus. This place, then, (if it can be thought of as an angle) would be the third angle [angulus lateralis] of the scapula, since we count as the first angle [angulus superior] (Z in figs. 1, 2, 3) the upper angle of the base, and the lower the second angle [angulus inferior] (Y in figs. 1, 2, 3).

Three angles of the scapula; a fuller description of the sides
Those two sides which make the third angle at their ends differ not only in the shortness of their course, but also in their thickness. The higher the lower side [margo lateralis] runs upward from the base, the thicker it becomes, and noticeably more dense (at P in fig. 1 and S in fig. 2), just as if by means of this side Nature had wished great strength added to a scapula that is otherwise thin and weak, and in the second place had prepared a convenient place for the origin of certain muscles. 29 For besides the fact that the thickness of this side makes the inner part of the scapula [facies costalis] (between N, O, P, and p in fig. 1) more concave for the sake of certain muscles [m. subscapularis] (as I shall soon add) and forms a kind of depression [facies dorsalis] (between G, H, S, T in fig. 2) on the outer side or protuberance, this side itself also effects a compression (T in fig. 2) in its outer surface near the lower angle of the base of the scapula and runs some way downward to provide an origin there for the muscle [m. teres major] (K in the 8th table of muscles, s in the 13th) by which the upper arm, when extended away from the chest, is brought back. Also, on the inner surface of this side next to its upper part where it abuts the neck of the scapula, there is also seen a somewhat rough and uneven oblong depression [tuberculum infraglenoidale] (Q in fig. 1) providing a point of origin for the muscle [m. triceps brachii, caput longum] (T in the 12th table of muscles) which we shall state in the second book begins from the scapula and makes the ulna extend. We shall always call this lower side of the scapula the lower “rib,” costa, as did the ancients, who called the upper and lower sides of the scapula pleurai/. 30 The upper side of the scapula is thin and not at all heavy all the way to the upper region [angulus lateralis] of the scapular cervix [collum scapulae] (C in figs. 1 and 2) where the inner process [p. coracoideus] of the scapula (F in figs. 1 and 2) originates; 31 this is where the upper side of the scapula thickens markedly. Within this side near the base of the scapula’s interior process, a certain depression (a in fig. 1) or half a foramen [incisura scapulae] is carved like a semicircle, providing a path for a twig [n. suprascapularis] (i in fig. 3, ch. 11, Bk. 4) of one of the fifth pair of nerves 32 of the dorsal medulla; this twig goes to the posterior surface of the scapula [facies dorsalis] together with a small vein [v. suprascapularis] and an artery [a. suprascapularis].

The neck of the scapula
The neck of the scapula [collum scapulae] (C, D in figs. 1 and 2), which is between the ends of the upper and lower sides of the scapula, 33 is thick and the scapula itself appears compressed at that point from its wide, thin area and thickened along its latitude. But the longitude or interval of the neck (from C to D in figures 1 and 2), which I measure from the upper part of its body to the lower, greatly exceeds its thickness, which extends from the anterior to the posterior.

The depression made to receive the humerus
The neck continues to be extended considerably outward, and is widened; being itself oblong, it forms an oblong depression [cavitas glenoidalis] (A, B in figs. 1 and 2), ending with a circular edge in the lower part but extended more to a point in the upper part. This happens because of an impression (C in fig. 1) made here in the inner surface of the neck to make room for the tendon of the muscle [m. subscapularis] (G in the 7th table of muscles, H in the 8th) which rotates the arm inward and anteriorly. The upper part (A in fig. 1) of the scapular neck and socket extends higher so that two very strong ligaments of this joint [ll. glenohumeralia] (e in the 5th table of muscles and V in the 13th) may better take their origin from this point, and so that the outer head (m in the 6th table of muscles) of the muscle [m. biceps brachii, caput longum] that will be considered the anterior of those that flex the forearm may conveniently take its origin hence. This scapular cavity is covered with cartilage like the other joint sockets, and is not carved very deeply. Its length and breadth do not match the length and breadth of the head of the humerus (A, B, C in figs. 1 and 2, ch. 23) with which it is articulated. 34 Nature devised this feature in quite a peculiar way in this joint. In other joints, the heads match the sockets perfectly, unless you wish to make an exception of the joint of the femur with the tibia [articulatio genus] (join E, F, I of fig. 1 ch. 30 with G, F, I of fig. 7 ch. 31 and consult fig. 8 of the same ch.), where you will understand the sockets of the tibia do not match the heads [condylus medialis, c. lateralis] of the femur, and that Nature was making some separate arrangement in that joint as well. We shall explain in the appropriate place where the knee differs from the system of the other joints, but now we must explain the shoulder joint.

The cartilage which often augments the socket of the scapula
Since Nature carved out this depression of the scapula rather lightly for the sake of loose movements and made it not very wide or long (in addition to special ligaments of this joint,

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which we shall discuss in the second book together with the muscles, and certain processes of the scapula which you shall hear prevent dislocations of the joint 35 when we describe those too in the course of our account), she many times fashions in this depression a certain cartilage [c. fibrosa] made like a ligament [labrum glenoidale] by which she increases the cavity, makes it deeper, and substantially corrects its excessive propensity for dislocation 36 without at the same time obstructing the very loose and different motions of the arm which we very much need. This cartilage is put around the cavity, attached neither to the scapula nor to the humerus, linked only to the ligaments [ll. capsularia] surrounding and embracing the joint. The outer surface of this cartilage is thick, gradually thinning toward the middle of the cavity; it ends well short of the center, as if someone were increasing the cavity’s circumference with a ring whose shape had been forged into a triangle whose outer side faces the outer circumference of the joint and whose inner side rests in the cavity; above, it faces the head of the humerus, 37 so that two of its angles touch the circumference of the joint while the third faces the center of the cavity. 38 You will readily see this product of Nature’s diligence, so delightful to behold, in quadrupeds and birds even if a human body is not at hand, since the cavities of the tibia bone are always enlarged by the same artifice [menisci medialis at lateralis]. By virtue of this cartilage, whenever it is found, the cavity of the scapula is deepened and at the same time the cartilage readily yields to impact and compression of the bones without restricting the free movement of this joint.

Processes of the scapula
There are two processes by which Nature provided for this joint. One of them is the upper one [acromion] (K in figs. 1, 2, 3), and we shall call it the summus humerus; presently it will be explained that it originates from the spine of the scapula (G, H in fig. 2).

The inner process
The other [processus coracoideus] (E, F in figs. 1, 2) is inner and smaller; it takes its beginning from a broad root (F in figs. 1, 2) on the upper side of the neck of the scapula and from here, quite wide, it is brought forward opposite the anterior part of the joint more toward the top. The lower part of this process is quite smooth, and concave like the ancient Greek letter C 39 , and for this reason is also called sigmoeidh/j, sigmoid. 40 Others, however, from the appearance that an anchor presents that has one part fixed in the ground, have called this process a)gkuroeidh/j. 41 Many, on the other hand, because it is inclined like a crow’s beak, have called it kwrakoeidh/j, coracoid. 42 Galen’s translators have subsequently made a mockery of these names — with assistance from Galen, since he is inconsistent in his nomenclature; for while elsewhere he almost always calls this process ancyroid, in the thirteenth book of De usu partium he applied that name to the scapular process which we call the top of the shoulder. 43 But the names of this process will necessarily come up later. But now we shall run through what remains to be told about the interior process [p. coracoideus]. On its lower surface it is smooth, but above it is rough and uneven. It looks thicker on the upper part of its beginning, and bulges in an irregular swelling (F in figs. 1 and 2) against which the clavicle nearly rests and is firmly attached. 44 On its tip (E in figs. 1 and 2), where it puts forth an epiphysis, it is also rough, so that the inner head of the anterior of the muscles that flex the forearm [m. biceps brachii, caput breve] (n in the 6th table of muscles) may better take its origin from it, and so that the ligament [l. coraco-acromiale] peculiar to the shoulder joint may have its beginning here. Between the tip and the tubercle on which the clavicle is nearly supported 45 (f in fig. 1), this upper surface of the process is also rough so that the ligament [l. coraco-acromiale] (c in the 5th table of muscles) leading from here to the upper process of the scapula may better be put forth. 46 Just as this upper surface of the process is rough so that it may put forth those ligaments 47 and that muscle’s head, 48 so too the neck of the scapula shows certain little blind foramina circularly arrayed, from which hangs the origin of powerful ligaments [capsula articularis, ll. gleno-humeralia] belonging to this joint.
Now it will be timely also to talk about the other process [acromion] of the scapula. We shall best discover its nature if we look carefully at the anterior and posterior surfaces of the scapula.

The anterior surface of the scapula, next to the ribs
The scapula is flat and concave on its anterior surface [facies costalis] (fig. 1) so as to fit the convexity of the ribs and while being fixed over them to be moveable as required, as well as to suit it to the muscle [m. subscapularis] (G in the 7th table of muscles, H in the 8th) which fills the entire anterior surface of the scapula and rotates the humerus inside and forward. This concave surface of the scapula is indeed smooth, but it is not even in all places; for next to its lower surface it puts forth certain tubercles (M, M, M in fig. 1) that stand out slightly as oblique lines 49 which make what amount to depressions, as if the ribs of the thorax on which this side of the scapula rests had been pressed into the scapula over time, and the scapula itself had taken on their outline by giving way. For these depressions and prominences appear more in the old than in children and youths, in whom everything protrudes and grows out less conspicuously. The anterior surface of the scapula protrudes somewhat at the root of the higher angle of the base (F in fig. 1), making a region suitable for the second of the muscles [m. trapezius] that lift the scapula (G, D in the 9th table of muscles) to be firmly inserted. 50 The anterior surface of the scapula, where it is opposite the base of the acromion (compare N, O in fig. 1 [fossa subscapularis] to H, G in fig. 2 [fossa infraspinata]) or the scapular spine, 51 is more markedly concave than elsewhere, as if when Nature had fashioned the spine of the scapula she had pulled the hollow 52 part of the scapula toward the posterior and thus increased its hollowness, in the same way we see it done in vessels of clay and other things that are daily made of casting material or wax. 53 For when we look at the handle which is put on the outer surface of a jar, the hollow part of the jar on the opposite side is observed to be more depressed as if pulled outward from the jar. This is seen especially

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in those surfaces where the thicker parts of the handle are located. By the same token, those points in the hollow of the scapula are likewise more impressed and hollowed which correspond to the ends of the spine. 54 Presently you will hear that along the entire surface where it arises, the spine is heavier at its ends than in the middle of its course. 55 Among the scapula’s other concave surfaces, the one that shows itself most concave is the one next to the neck of the scapula. For aside from the fact that the neck of the scapula (C, D in fig. 1) is posteriorly drawn out and gathered away from the scapular spine, it is also especially heavy and inwardly protuberant at this point, significantly increasing this cavity. In the same way the lower side (P in fig. 1) of the scapula also makes the hollow deeper because it is thick.

Posterior surface or dorsum of the scapula
The posterior surface of the scapula (fig. 2), furnished with a conspicuous, spiny process (G, H, I, K, L 56 in fig. 2), is convex if casually observed, for Nature would not have been unaware that this shape is better adapted to enduring injuries without harm. But if we study this protrusion of the scapula more closely, two concave surfaces will come to our attention that are perfectly suited to receive muscles. One [fossa infraspinata] (between G, H, D, S, T, and Y in fig. 2) lies beneath the spine of the scapula between the lower surface of the spine and the swelling, thicker part of the lower side of the scapula. The other [fossa supraspinata] (between Z, a, I, G, and especially between b and c in fig. 3) is between the upper surface of the scapular spine and the upper side of the scapula. A certain muscle [m. supraspinatus] (k in the 6th table of muscles, G in the 11th) occupies this surface; we shall declare it the third 57 of the muscles that rotate the arm. The lower cavity is filled by a muscle [m. infraspinatus] (G in the 11th table of muscles) which will be counted the second of the muscles that rotate the arm. 58 Although this outer or posterior surface of the scapula shows these two cavities on account of the spine of the scapula as well as its sides, nevertheless the whole (since it is seen to swell out) was called the back or dorsum of the scapula by the ancients, borrowing from its likeness to the actual human dorsum. Now the process that arises from this dorsum of the scapula 59 they called the spine for its resemblance to the posterior processes of the vertebrae, or spines, 60 and since these were quite rightly established as such by the ancients, I shall not stray so much as a fingernail’s breadth from these names. I shall call the outer surface of the scapula the dorsum, and the root of the acromion I shall call the spine of the scapula.

The shoulder top or a)krw/mion, whose careful description must now be commenced
I use the term summus humerus for what was named the acromion by the ancients, though it is not so easy to divine what anyone understood by this word. 61 If only because of the divine Hippocrates, this word should not be neglected, nor should a hasty decision be made regarding it; let us but call our minds away for now from syrups and juleps, 62 and reckon that the divine oracles of Hippocrates on fractures, dislocations of the bones, and such afflictions, 63 pertain to us also. It will not therefore have been out of place to describe the spine of the scapula and the acromion as seemed best to us, and afterward to add to our account the opinion of Hippocrates and Galen. A powerful, heavy process (G, H in fig. 2) grows from nearly the whole width of the dorsum of the scapula: not from the middle of the longitude of the dorsum (not midway between Z and Y in fig. 2, but more towards Z), but not far from its upper surface. This process (which is the spine of the scapula) gradually becomes larger and larger, and finally (H to K in fig. 2) leaves the dorsum of the scapula near the neck; appearing more or less smoothly rounded, it is brought slightly forward. It broadens noticeably (K in figs. 1, 2, 3) above the joint of the scapula where it joins the humerus and has a broad epiphysis which in children is constructed of several ossicles 64 (Q, R in the fig. for ch. 3) joined by cartilage. The entire anterior, posterior, and lower parts of this process are smooth and not at all rough, but its upper surface is by no means smooth but rough, with certain small blind foramina, particularly in the upper surface of its epiphysis and at a point (I in figs. 2, 3) not far from the base of the scapula where this process is thicker and often has an additional epiphysis. Surely, Nature did not devise them in vain: 65 she built these rough places for the sake of muscles; 66 in them is implanted a very large muscle [m. trapezius] (G, D in the 9th table of muscles) that draws the scapula upward. This process is rougher in the places I mentioned because the muscle makes a broader and stronger insertion there. Furthermore, this roughness provides the point of origin 67 for the most eminent muscle that moves the arm [m. deltoideus] (D in the 10th table of muscles), which anatomists have called e)pwmi/j 68 because it perfectly covers the joint [articulatio glenohumeralis] of the humerus with the scapula. In the anterior surface of the process 69 a depression [facies articularis acromii] (L in figures 1 and 2) is carved so lightly and superficially that you would scarcely distinguish whether it is a capitulum or a depression. Into this depression the slightly projecting tubercle of the clavicle [extremitas acromialis] (Q in fig. 3, ch. 22) is articulated, and is held in place by the strongest of ligaments. 70

Cartilage peculiar to the joint of the clavicle with the upper process of the scapula
Often at this place there intervenes a special cartilage [articulatio acromioclavicularis, discus articularis], quite similar to the one which we stated is observed in joints of the lower with the upper maxilla. 71 This cartilage is smooth and slippery on both sides where it faces bones; it is held in place and in contact only with the ligaments surrounding the joint. The part of the process just mentioned (G, H in fig. 2) which originates from the dorsum of the scapula and is (so to speak) next to the dorsum, is opportunely named the spine; it is observed also in dogs (C, D in fig. 4), sheep, and horses. But the part (from H toward K in fig. 2) which goes away from the scapula forward to the outside and gradually broadens, can be observed only in humans, apes, squirrels, and any other animal that has a clavicle, that part we shall call the summus humerus [acromion], borrowing this name from the Greeks, who no doubt named the joint of the humerus with the scapula w=)moj, and called this part of the process a)krw/mion because it constitutes the upper surface of the joint and was considered, as it were, that joint’s safest bulwark. Certainly this is always what one learns from Hippocrates, often in other places and especially when he says that the humerus (which he himself calls the braxi/wn) is not dislocated upward 72

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(no doubt because the acromion obstructs it), and when he writes about fractures of the acromion. 73 But here Galen must be heeded as well, in his book De ossibus which states that the joint [articulatio arcomioclavicularis] of this process (Q [clavicle] to l [acromion] in the skeletons) with the clavicle is called the acromion by a number of professors of dissection.

A third bone enumerated by Galen in the joint of the acromion with the clavicle
He also adds that some place here a third bone besides this process and the clavicle, in humans only, and that they call this “acromion” and kataklei/j. 74 In the thirteenth book of De usu partium Galen counts this third bone in humans and denies that simians have it; 75 likewise in his books De anatomicis administrationibus and in his commentary on Hippocrates’ De articulis. For he writes that besides this upper process of the scapula and the clavicle there is a third cartilaginous bone which is placed in the joint of the clavicle with that process of the scapula, and from it originate membranes and ligaments by means of which this joint is more strongly held together. In the fifth book of De anatomicis administrationibus Galen says that such a bone is called a)krw/mion by Hippocrates, and he himself calls it by that name in the same place, just as he testified in his book De ossibus that certain people place a third bone here and it is called by them a)krw/mion. But at the same time, he sometimes in his books De usu partium, De anatomicis administrationibus, and in almost all his commentaries on Hippocrates, he called this process of the scapula a)krw/mion, or at least the joint of this process of the scapula with the clavicle. I therefore wonder greatly at the inconsistency of Galen here and will wonder much more until I discover this third cartilaginous bone in man. For by no means do I believe that Galen considered the above mentioned special cartilage of this joint to be a bone, since cartilages of this sort generally resemble true cartilage less than the do ligament and are not by any means osseous, and furthermore since it is found in the ape as much as in man. Even if it were to be considered a bone, apart from the fact that Galen would have mentioned it differently and would have written that it occurs in the joint instead of being laid upon it, he would still not escape censure for not having established the peculiar bone 76 in the joint of the clavicle with the pectoral bone [sternum] (the larger part of the 4th fig. in ch. 22) and again in the joints of the lower maxilla with the upper (marginal fig. in ch. 10), 77 and in the knee 78 (fig. 8, ch. 31). Cartilages of that type [cartilago fibrosa] are in fact easier to find there than here in the acromion, but they seem to have been unknown to Galen and overlooked by him. It would therefore be much better now not to call this peculiar cartilage a bone (even if it were osseous), than tacitly to imply that so many bones escaped Galen’s notice. 79 I have so far never been able to find a third bone here, for all my diligent dissection with Hippocrates in mind. 80 I think it is clear enough that Galen never saw it either, and should I dare venture so far in impiety toward him, I would affirm that he invented a bone of this sort from its similarity to bones which resemble a sesame seed [ossa sesamoidea] (V, V in fig. 1 ch. 25, y, w in fig. 2, ch. 33), which 81 you will learn are put in front of joints and junctures of other bones in the same way Galen gave out that a cartilaginous bone is situated here. I will gladly therefore admit that I have found this third bone no more in man than in ape, nor has anyone been present when I was dissecting where one was observed by even a single person, though I always adminish all present to watch closely for it. 82 And accordingly if someone shows me this bone or anything like it in addition to the process of the scapula and the clavicle (Q and l in the skeletons), I assure him I will more quickly demonstrate something else of that kind in the joint [articulatio glenohumeralis] of the humerus with the scapula that is far worthier of close consideration and intensive study. For this reason only, I now knowingly pass it by.

The only animals in which the upper process of the scapula exists
At the same time I wish all to know that I have never encountered any animal possessing this process of the upper scapula except man, ape, squirrel, and, if I remember rightly, the dormouse. I therefore have no doubt that whoever first wrote that only man possesses an acromion understood that man alone had this process; when he saw no upper process of the scapula (but only the spine) in dogs, 83 sheep, goats, rabbits (which indeed have only the inner process of the scapula) and other quadrupeds that are served as food, he did not bother with apes, as Galen did. We may therefore call this upper process of the scapula summus humerus or “the upper process” until a more correct view comes to light. 84

The use of the acromion
We shall explain better for what use the acromion is given to humans and other animals possessing clavicles when we have begun our account of the clavicles. For besides the fact that this process prevents an upward dislocation of the shoulder, it is an extremely safe bulwark for the shoulder joint, and serves perfectly for the origin and insertion of muscles [mm. deltoideus et trapezius]; it is most of all helpful, when the clavicle is attached, in holding the shoulder joint as far as possible from the sides and ribs of the thorax, and keeping it in a place which it most requires for those quite various and different motions that it performs. 85 These matters will be resumed at greater length in the descriptions of the clavicles, for it will soon be time to put a limit on our discussion of the scapulae, especially as nothing else remains to be explained except perhaps something quite small. Such a thing could be that the base of the scapula, where it is equipped with epiphyses, is quite spongy and porous. Several foramina [canalis nutriens] extend into the spine of the scapula, carrying veins to it (since it is thick) to supply it with nutriment. One (c in fig. 3) is often seen in the broad part [fossa supraspinata] that is formed by the upper side of the scapula and its spine, and another on the inner surface of the scapula where it is more deeply hollowed.

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]