[Figures of Chapter 22]

Legend of the three preceding figures and their characters
The first figure of the present chapter represents the clavicle of the right side in its anterior or outer and superior aspect.

The second shows the posterior or interior face of the clavicle of the right side, together with its superior aspect as well.

The third displays the inferior aspect of the clavicle of the same side.

A 1 , 2 , 3	Capitulum [extremitas sternalis] of the clavicle, by which it is articulated to the pectoral bone [sternum].
B 1	First angle [ventralis] of this capitulum.
C 1 , 2 , 3	Second angle [dorsalis] of the capitulum.
D 1 , 2 , 3	Third angle of the capitulum just mentioned. In the first figure, the entire circumference of the triangular capitulum is visible with the letters B, C, and D, 1 just as in the figure placed here above D in the character index for the sake of clarity.
E 1 , 3	In the anterior surface of the clavicle, a protuberant line is marked directly aligned with the first angle, marked B.
F 2 , 3	In the third figure, F and G mark the protuberant line on the lower surface of the clavicle, which F and G in the second figure also show.
G 2 , 3	G separately indicates the roughness [impressio ligamenti costoclavicularis] appearing behind the line marked F.
H 1 , 2	The middle of the longitude of the clavicle [corpus claviculae], which would be smoothly rounded but for the line (F) in its lower part.
I 1 , 2	At this point the clavicle broadens as it goes toward the upper process of the scapula, and it protrudes on its upper surface (which is also marked I to K).
K 1	Roughness visible on the surface of the clavicle where it is most concave in its anterior part. 2
L, M 3	Slightly concave lower region of the wider portion of the clavicle, rough but not convex like the upper part. 3
N 3	Here too the clavicle is rough [sulcus musculi subclavii], as it is next to M; from here a ligament [l. coracoclaviculare] runs to the inner process [p. coracoideus] of the scapula.
O 2 , 3	Area of the clavicle most protuberant backward or inward, and the bulge [tuberculum conoideum] peculiar to this location.
P 3	A particularly rough spot visible in the lower part of the clavicle where it is articulated to the upper process [acromion] of the scapula. 4
Q 1 , 2 , 3	In the third figure Q marks the tubercle [facies articularis acromialis] by which the clavicle is joined to the upper process of the scapula. In the first and second figures, Q marks the location of this tubercle.

Number of the clavicles
There is a single clavicle (Q to O and l in the skeletons) (the Greeks call them klei=dej, the Latins furculae or iugula) ⁷ on each side, attached to the pectoral bone and the acromion or upper process of the scapula.

Their articulation to the pectoral bone
The clavicles are articulated to the pectoral bone [manubrium sterni] by depressions [incisura clavicularis] (r in fig. 7, ch. 19) which we have said are carved out in the sides of the topmost part of the first bone. Just as those depressions are oblong, running from the anterior parts posteriorly downward, wider on the anterior than the posterior, and higher on the inner side than on the outer, so also are the heads of the clavicles [extremitas sternalis] (A in figs. 1, 2, 3) which are connected to the pectoral bone. These are oblong like the depressions ⁸ [facies articularis sternalis], and depressed; if one paid careful attention to their circumference, he would judge that it is more or less triangular. One angle (B in fig. 1) is in the anterior part of the head toward the bottom, quite blunt. The second (C in figs. 1, 2, 3) is also blunt, visible in the upper part of the head somewhat toward the posterior. The third (D in figs. 1, 2, 3) is more acute and longer, located in the posterior region and angled downward. As these angles are obtuse, the lines of the triangle are irregular and deflected outward. The one that runs from from the first angle to the second (from B to C in fig. 1) is the shortest; the one from the second angle to the third (from C to D in figs. 1, 2, 3) is much longer; the one from the first to the third (from B to D in fig. 1) is the longest of all, and curved. Such is the circumference of the clavicle’s head; it is coated with a large amount of cartilage [cartilago articularis], and smooth. But when the cartilage is broken away together with the very thin epiphysis, the head is rough and uneven.

The special cartilage of the joint of the clavicle with the pectoral bone
Though the head of the clavicle abounds in cartilage [c. articularis] no less than the depression of the pectoral bone, Nature has fashioned a cartilage here (S in fig. 4) like the ones which we have said elsewhere are placed in the joints of the lower maxilla with the upper ⁹ [articulatio temporomandibularis, discus articularis]. Between the depression of the pectoral bone [manubrium sterni, incisura clavicularis] and the head of the clavicle there is a cartilage [discus articularis] as large as the space between the head and the depression. It is thin everywhere and of equal thickness throughout; ¹⁰ where it faces the depression it is quite smooth and coated with an oily humor, ¹¹ and it is nowhere attached to the depression or the pectoral bone. Likewise, where it touches the head of the clavicle it is similarly smooth and slippery, and attached not to the head but only to the ligaments ¹² surrounding the joint. This cartilage is no less triangular than the head of the clavicle that is articulated to the pectoral bone.

The marvellous curvature of the clavicle
From this joint [articulatio sternoclavicularis] with the pectoral bone, the clavicle extends by no straight course to its other joint [art. acromioclavicularis] (at Q in figs. 1, 2, 3) by which it is connected to the upper process of the scapula. As it proceeds from the pectoral bone (from A to H in figs. 1 and 2) it curves gradually outward, becoming convex in its anterior part and concave in its posterior. But there (from H to Q in figs. 1 and 2), after the midpoint of its length, it proceeds in an opposite course, curving and becoming convex on the inside, but concave on its anterior surface. It bulges prominently forward where it is closest to the superior process of the scapula, thus becoming twice convex and twice concave. The part ending at the pectoral bone, also called parasfagi/j, ¹³ extends more to the back, or to the inside of the thorax; the part articulated to the upper process of the scapula, also called the e)pwmi/j, ¹⁴ moves forward and outward from the inner part of the thorax as the clavicle changes course midway. Thus it is convex in its anterior part, in the anterior part of the chest not far from its joint with the pectoral bone, and concave in its internal part. Not far from the acromion, its anterior part is concave with a very short curve, but in its posterior region bulging and convex. To express briefly a subject that must be considered carefully because of frequent dislocations and fractures of the clavicles, the course of the clavicle resembles our letter ∫ , especially if we imagine it curved a little more in mid-course like a capital S, thus: {Sclav.gif}.

The use of curvature ¹⁵
None of this was done idly or in vain by the Maker of things; for where the clavicle faces the throat, it is rightly concave on its posterior or interior side, as ¹⁶ the rough artery [trachea], the esophagus with the nerves of the sixth pair of cerebral nerves, ¹⁷ and especially the noteworthy series of nerves ¹⁸ going from the dorsal medulla to the axilla, need to pass this way. ¹⁹ For these nerves especially the clavicle provides a path, and it is placed before them like a bulwark. Because the clavicle extends to the posterior from the throat, or rather from the middle of its own length, and did not for any purpose need to be convex on its anterior surface, it necessarily curves forward again next to the upper process [acromion] of the scapula until it reaches the part of that process (L in figure 1, chapter 21) to which it can fitly be articulated. Here it extends forward as much as it had diverged backward ²⁰ in the protruding part [tuberculum conoideum] (O in figures 2 and 3) of its posterior surface, which is not far from the acromion.

Why the shoulder joint is kept away from the ribs; the use of the clavicle and acromion ²¹
For if the clavicle ran only posteriorly from the midpoint of its length [corpus claviculae], going out to the sides of the neck, and did not articulate with the upper tip [facies articularis acromii] of the scapular process, surely nothing would prevent the whole scapula, being unsecured by the clavicle, from falling over the thorax and being pressed against the side of the thorax, and the shoulder joint becoming extremely close to the ribs (you may find these in the skeletons where the joint of R with S is removed from the ribs by the joint of Q and l), and thereby a great many motions of the arm would be inhibited. For the arm is able to be moved in such a variety of different motions in man, in monkeys, and all the animals that have clavicles, because its joint with the scapula

The connection of the clavicle to the acromion
The clavicle is articulated to this process by a scarcely projecting tubercle ²³ [extremitas acromialis] (Q in fig. 3), wider than it is long, and rather oblique; such an articulation takes place here [art. acromioclavicularis] that you can scarcely distinguish whether the bone receives or is received. This is the type of joint that we have said the Greeks called a)rqrwdi/a. ²⁴

Composition, protuberances, rough and smooth places, and foramina of the clavicle
The part of the clavicle which is connected to the upper process of the scapula (from I to Q in figs. 1 and 2) is rather wide, as the process is also wide and ample. This part of the clavicle, like the part joined to the pectoral bone, is porous and more loosely knit than the remaining portion of the clavicle, ²⁵ as those parts are thicker and denser: bones are always seen to be more spongy inside the thicker and bigger they are. The clavicle itself is extremely solid in the middle of its length (H in figs. 1, 2, 3) [corpus claviculae] because here too it is thinnest and more or less smoothly rounded. But it is not entirely smooth, for in its lower region it protrudes as in a line [impressio ligamenti costoclavicularis] (F, G in figs. 2 and 3) ²⁶ which begins not far from the head of the clavicle [extremitas sternalis] which is articulated to the pectoral bone, near the midpoint between the posterior and anterior angles (C, B) of its head. This line ²⁷ extends a little beyond the middle of the clavicle’s length [corpus claviculae], and is provided so that the first of the muscles that move the thorax [m. subclavius] (d in the 4th table of muscles) may take its beginning from there. Near the beginning of this line by the head of the clavicle [extremitas sternalis] there is seen a concave roughness (G in figs. 2 and 3) from which originates a strong ligament [l. costoclaviculare] that binds the clavicle to the pectoral bone [manubrium sterni] where the cartilage of the first rib of the thorax is attached (C in fig. 1, ch. 19). At the other end of this line there is another roughness [sulcus musculi subclavii] (N in fig. 3) and a certain roughish depression where the clavicle nearly rests upon the tubercle (F in figs. 1 and 2, ch. 21) and the root of the inner process of the scapula [p. coracoideus], from whence a ligament [l. coracoclaviculare] is put forth that firmly binds the clavicle to that tubercle. The lower surface of the clavicle where this line ends, and the clavicle itself, are wide, concave, and rough (from L through M to Q in fig. 3), particularly next to the connection ²⁸ of the clavicle to the upper process [acromion] of the scapula where the ligaments binding this joint originate more strongly than on the upper surface. The upper region of the entire clavicle is quite smooth except near the joints, where it is somewhat rough in order to put forth ligaments, and likewise for muscles. From the upper part of the clavicle near the pectoral bone, the muscle [m. sternocleidomastoideus] (Q in the 4th table of muscles) originates which also begins from the pectoral bone and is implanted in the mamillary process [p. mastoideus] of the head (k in figs. 3, 4, 5, chapter 6) and will be counted the thirteenth ²⁹ of the movers of the head or one of the seventh pair. To the upper part of the clavicle that is joined to the upper process of the scapula, that muscle [m. trapezius] (G in the 9th table of muscles and b in the 4th) is inserted ³⁰ which will be numbered the first of those that elevate the scapula. In the anterior part of the clavicle at the root of the first angle of its head, a line (E in figs. 1 and 3) also protrudes which ends before the middle of the clavicle’s longitude; from it a major portion of the muscle [m. pectoralis major] (D in the 3rd table of muscles, then from K to L) ³¹ that adducts the arm to the chest takes its origin. In addition, on the anterior surface of the clavicle where it is bent to the rear and where it is concave not far from its articulation with the upper process of the scapula, there is also a noteworthy roughness (at K in figure 1) prepared for the muscle [m. deltoideus] (from e to f next to C in the 4th table of muscles) ³² that raises the arm, a large part of whose origin begins here. On the posterior surface of the clavicle there is nothing uneven which has not been mentioned except a certain tubercle [t. conoideum] (O in figs. 2 and 3) protruding here where the clavicle is most convex; this tubercle constitutes as it were an angle of that bulging surface, and it puts out a ligament [l. coracoclaviculare, pars conoideum] to the inner process of the scapula. Beyond these things there is scarcely anything noteworthy in the clavicle, unless perhaps you wish some small not quite pervious foramina to be added to the account. Sometimes two, sometimes three of these are seen in the densest part of the clavicle, especially in the posterior surface, provided to transmit the small veins that nurture the clavicle.