[Figures for Chapter 10]
Key to both figures of the tenth chapter, and their
The first or right [left] 1 figure of this chapter shows the lower maxilla [mandibula] together with the teeth in their anterior aspect. The second figure displays the lower maxilla along with the lower set of teeth drawn in the posterior view. The picture at the beginning of the third chapter of this book at the letter C illustrates the maxilla from the side.
|A 1 , 2||One head [processus condylaris, caput mandibulae] of the lower maxilla, by which it is articulated to the upper maxilla 2 [os temporale, fossa mandibularis].|
|B 1 , 2||Cervix or neck [collum mandibulae] of the head marked A.|
|C 1 , 2||Acute process [processus coronoideus] of one side, into which the temporal muscle builds its insertion.|
|D 2||Hidden in the shading, D marks the large depression in the left [right] figure into which is inserted the muscle hidden in the mouth [m. pterygoideus medialis] which serves with the temporal and masseter muscle to lift the jaw. 3|
|E 1 , 2||Roughness [angulus mandibulae] visible at the posterior and lower part of the maxilla, into which the masseter muscle is inserted.|
|F 2||In the shadowing of the left [right] figure, F marks the foramen [foramen mandibulae] that admits a branch [n. alveolaris inferior] of the third pair of cerebral nerves [nervus trigeminus, n. mandibularis].|
|G 1||Foramen [foramen mentale] by which a small branch [n. mentalis, rami labiales]of the nerve just mentioned drops forward into the lower lip.|
|H 2||On these tubercles [spina mentalis superior et inferior] are implanted the muscles [musculi geniohyoidei] 4 that draw the jaw downward; certain muscles [mm. genioglossi] of the tongue also originate from these.|
Man has the shortest jaw
Of all animals, man has the shortest lower maxilla in proportion to the total size of his body, while the ass and the horse generally have the longest among quadrupeds. 5 For man has a round face, not long, as with the other animals which, because they have no hands, stoop to feed. 6 But it was fitting that a hard jaw be made for humans, as for the other animals, because it alone moves and undergoes a variety of very powerful motions in biting and chewing (the 6th table of muscles shows the maxilla cut through the middle). So that such a hard, solid jaw should not by its excessive weight overburden the muscles that move it, it forms hollows [canalis nutriens, canalis centralis, canalis perforans] and noteworthy cavities [cavitas medullaris] filled with marrow, and it is at the same time free of any epiphysis. These hollows are not carved out in the posterior part of the jaw as they are in quadrupeds, but are farther forward toward the region of the chin, and at the sides.
The human jaw is made virtually from a single bone
In most animals, the maxilla consists of two bones at the end of the chin where the jaw
Two processes on both sides of the maxilla
The lower maxilla comes to an end on both sides in two processes, one of which [processus coronoideus] (C in figs. 1 and 2; A, B in the 6th table of muscles) is drawn to a point and very strongly receives the insertion of the tendon of the temporal muscle [m. temporalis], being completely covered by that tendon. The other process (A, B in figs. 1 and 2) [processus condylaris], which is posterior, ends in a transversely elongated capitulum [caput mandibulae] which articulates with a similarly shaped socket [fossa mandibularis] (h in fig. 5, ch. 6) carved in the temporal bone near the root of the jugal bone [pars squamosa, processus zygomaticus] and the anterior part [pars tympanica] of the organ of hearing. On this socket [articulatio temporomandibularis], and on the capitulum of the maxilla, cartilage [cartilago fibrosa] is laid like a crust.
Picture of the special cartilage in the joint of the maxillae
Foramina of the maxilla
In addition, the lower maxilla has two foramina on each side; one (F in fig. 2) [foramen mandibulae] is seen in its inner region not far from the processes just mentioned, the other (G in fig. 1) [foramen mentale] on the outer surface near the root and the side of the lower lip. The inner one, which is both larger and uneven or rough, 15 provides a path for a portion of the nerve [n. mandibularis, n. alveolaris inferior] of the third pair of cerebral nerves [nervus trigeminus] that is distributed to the roots of the teeth (T in the 2nd fig. preceding ch. 2, Bk. 4), along with the small vein [vena alveolaris inferior] and the artery [arteria alveolaris inferior] which enter this foramen to nourish the teeth and lower maxilla. The outer foramen lets a branch of this nerve (V in the figure just mentioned and G in the 5th table of muscles) [nervus mentalis, rami labiales] pass from the maxilla into the lower lip, and it is much smaller than the one on the inside. If you insert a hair into the internal foramen [foramen mandibulae] of a dried jawbone, you will see it move 16 easily from this foramen to the outer one [foramen mentale], and if you break open the jawbone you will observe a continuous path carved like a canal [canalis mandibulae] from one foramen to the other.
Alveoli of the teeth
Besides these foramina in the outer surface of the jaw, you will find no others at all unless you are willing to count the alveoli and their little compartments [alveoli dentales], in which we shall soon explain the teeth are fixed like nails. That the lower maxilla is thicker because of these sockets and hollows is best established by the fact that in old people, those whose teeth have been extracted, and in whom the tooth sockets have filled in, the jaw becomes much thinner and narrower from the bottom up. 17
Breadth, thinness, depressions, and rough spots in the posterior area
of the jaw
Where no teeth are fixed in the jaw, and in that place where it puts out the processes just mentioned, the maxilla looks very wide, and, if you examine the sides, quite thin, carved inside (D in figure 2) and outside (E in figures 1 and 2) [angulus mandibulae] with a kind of wide depression, indented on the surface only, so that the muscles other than the temporal muscle that elevate the jaw 18 might better fit in their insertion [tuberositas masseterica, tuberositas pterygoidea], and so that the muscle that is hidden in the mouth (D in the 6th table of muscles) [musculus pterygoideus medialis] might crowd the narrow part of the pharynx [pars nasalis pharyngis] less with its thickness and mass. Accordingly, the jawbone is rightly hollowed on the inside more than on the outside. Indeed, it is characteristic of this wider surface of the maxilla that it is rough and uneven especially near the inferior and posterior region of this part (E in figs. 1 and 2). The Maker of things contrives this for the insertion of muscles, not unaware that something adheres and attaches more readily to rough and uneven places than to level and smooth ones. It is also for this reason that the inside of the maxilla near the chin swells with a number of tubercles or rough places (H in fig. 2) [spina mentalis superior et inferior] so that the muscles by which it is drawn downward (H and I in the 5th table of muscles) 19 might achieve a stronger insertion, and finally so that several peculiar muscles of the tongue (H in figs. 1 and 2, ch. 19, Bk. 2) [musculi genioglossi] might better fit their origin here. Something of this sort also happens on the outer surface of the lower maxilla around the tip of the chin so that the muscles of the lower lip 20 (N in the 4th table of muscles) may more easily originate from there.