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 17 On the Lumbar Vertebrae

[Figures of Chapter 17]

Key to the Three Figures of the Seventeenth Chapter and Their Characters
Since all the lumbar vertebrae take the same form, we have illustrated here only one of them, in three aspects. In the first figure we present the vertebra's anterior aspect, in the second the side, in the third the posterior aspect.

A 1 , 2 , 3 Superior epiphysis of the vertebral body.
B 1 , 2 Inferior epiphysis of the vertebral body. 1
C, D, E, F, G These letters, not all visible in same figure, mark the spine [processus spinosus]; each shows a separate feature in the spine as follows:
C 1 , 2 , 3 Superior portion of the spine of the lumbar vertebra, or its wide, rough line.
D 2 Hidden in the shading below the spine in the second figure, D marks the inferior line of the spine.
E 2 Not far from D, E marks the depression of one side, lying to the side of the line marked D.
F and G 2 , 3 Epiphysis of the spine, resembling a triangle whose base is labeled G and acute angle F. 2
H 1 , 2 , 3 Transverse process [processus transversus] of one side.
I 1 , 2 , 3 Ascending process [processus articularis superior] of one side.
K, L, M 2 , 3 Ascending process of the other side, labeled more expressly: K marks the depression [facies articularis], L the anterior lip or brow of this depression, M the posterior brow [processus mammillaris].
O 2 , 3 Descending process [processus articularis inferior] of one side. In the third figure, it marks the tubercle or head of the process. 3

So that you may follow more easily the location and form of the processes to be described separately in this chapter, we have shown in this figure the lumbar vertebra of a caudate monkey from its right side, where A and A mark the vertebral body. B is the transverse process, here clearly facing upward. C marks the spine, which also

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slants upward. D and E show the two ascending processes, F and G the two descending processes. Finally, H marks the process [p. accessorius] which (as you will soon hear) human lumbar vertebrae lack. 4
We have already gone over nearly everything having to do with the lumbar vertebrae; rather than linger too long in their description, we shall summarize the facts previously mentioned and add whatever special information this chapter calls for.

What the bodies of the lumbar vertebrae are like
The lumbar vertebrae (E-F on the fig. in ch. 14, L-M in the skeletons) are five in number, the largest and thickest of all we have described so far, and therefore their bodies are also filled with many foramina; these do not lead anywhere, and exist only as vessels providing nutriment.

The foramina
The foramen [f. vertebrale] carved out for the dorsal medulla in these vertebrae is smaller than the ones in the vertebrae that rest upon them to the degree that the dorsal medulla becomes narrower and thinner (E-F in fig. 1, ch. 11, Bk. 4) over its entire length because of the nerves that lead off from it. The foramen [f. intervertebrale] (Q in the fig. for ch. 14) carved on both sides of the vertebra to let out a nerve and to admit a vein and an artery is almost entirely made by the higher vertebra which forms its top and sides, while the vertebra below forms only the lower portion of the foramen.

The transverse processes
The transverse processes of these vertebrae (H in figs. 1, 2, 3), one on each side, are much thinner than those of the thoracic vertebrae (H, I in figs. 1 and 2, ch. 16). But at the same time they are quite extended as if to perform the function of ribs in the loins. The first and fifth lumbar vertebrae have shorter transverse processes than the middle ones (this is shown in the first skeleton). 5 In none of them do the transverse processes angle visibly upward, save those of the fifth vertebra: the bones of the groin [os ilii] (Q and o in the first skeleton) prevent these from being extended transversely like the others. Those bones come closer to that vertebra than the length of the transverse processes in the middle lumbar vertebrae.

The spine
Their spine (C, D, E, F, G in fig. 2) is strong and thick, and proportionally to the mass of these vertebrae not very tall or long. If you look at the left and right it is thin, but if you consider its top and bottom (figure 2, from C to D) it is very wide. It is sharp above (C in figs. 1, 2, 3), ending in a rough line, but thicker below and having two depressions, as it were (D is the line in fig. 2; E marks one of the depressions), in the middle of which a line or long tubercle 6 is produced from which a ligament runs to the upper line on the spine of the vertebra beneath. This ligament [ll. interspinalia] fills the interval between the spines and separates the right muscles from the left 7 in the same way as the ligament (V in the 7th table of muscles) [membrana interossea] between the ulna and the radius more or less divides the inner muscles of the forearm from the outer. There is a point 8 (F, G in figs. 2 and 3) on the epiphysis of the spine as there is on the spines of the thoracic vertebrae; it is quite blunt, and looks somewhat triangular if you place one leg of the triangle at either side and the third (which is shorter 9 than the others) at the base of the spine’s epiphysis.

Ascending processes [zygapophysis superior]
The ascending processes (I, K in figs. 1, 2, 3) have a deep depression [facies articularis] (K in figs. 2, 3) on their inner side where they face each other and, if you pay attention to the anterior and posterior parts of the depression, oblong. 10

Descending processes [zygapophysis inferior]
The descending processes (N, O in figs. 2, 3) run conspicuously downward and end on their outer side in an oblong tubercle 11 (O in fig. 3) which faces more toward the vertebra’s front than its rear. These tubercles enter the ascending processes of the vertebra beneath, as I previously explained at greater length; nothing has been added thus far to this chapter that I have not said before. 12

The extra process which Galen ascribes to the lumbar vertebrae
I should add nothing else, had Galen not assigned an extra process (H in fig. 4) [p. accessorius] 13 on each side to the lumbar vertebrae which, he writes, 14 runs downward and is located next to the foramen [f. intervertebrale] through which a nerve runs that begins from the dorsal medulla. I have never observed this process in human vertebrae; consequently, in investigating it I decided I should employ the same system and method by which I regularly investigate features described by Galen that I do not find in human anatomy, and which I perceive to be other than he stated. My practice is to examine all of these in dumb animals, especially dogs (of which there has never been a shortage); 15 these have quite often shown me what Galen described, or instructed me what he meant as if leading me by the hand. I was unable to find this lumbar process until I undertook the complete dissection of an ape at Bologna for Giovanni Andrea Bianchi, 16 and assembled its bones together with those of a human skeleton.

The hospitality of Giovanni Andrea Bianchi
This man, a very celebrated professor of Hippocratic medicine at Bologna, brilliant as he is and utterly devoted to the students at his university, 17 had invited me a second time to Bologna to teach the human fabric and received me in his own home with all humanity and great generosity. Now in the lumbar vertebrae of apes near the base of the transverse process (G in fig. 4 18 ) on its lower surface is seen a sharp process (H in fig. 4) extending straight down and a depression cut for a nerve, making up its outer side and forming a kind of interval with the descending process into which the ascending process of the vertebra beneath enters. 19 Though it will not be possible to investigate the nature of this process in the ape for lack of a specimen, study the dog’s three lower thoracic

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vertebrae, which also have the same kind of process [p. accessorius]; in older dogs we see that such a process is always present in the lumbar vertebrae. But in the human, not so much as a sign of this process is found in any vertebra.

Number of processes in the lumbar vertebrae
Thus the lumbar vertebrae in humans have seven processes: one in the posterior or spine, two transverse, two ascending, and two descending. Simians have two more, which we have said are next to the roots of the transverse processes, so that they have nine processes. Some have counted that many in man by subdividing each of the ascending processes into two by virtue of the depression [facies articularis] between them (those two would be M, L in figs. 2, 3; the depression is K). But by this logic there would be eleven processes growing in the lumbar vertebrae of simians. Moreover, we should not fail to mention that Galen, inconsistently describing the foramina hollowed out for the nerves in the thirteenth book of De usu partium, does not seem to imagine a special process in the lumbar vertebrae when he attributes to the descending processes of the lumbar vertebrae the function which he elsewhere attributed to the process that we have said is simian. 20

Appendix: the 1555 ending of Chapter XVII (See note 19 above)
But the especial use of this process is not that it is created mostly to protect the nerve running in front of it from injury and to act as a bulwark for it. 21 It is built for a special muscle (you will find it by dissecting a monkey or a dog) which monkeys have in common with dogs and which humans, who do not bend the lower part of their back in a circle as much as those animals, lack so much as to have no sign of this process. // p. 96 // This muscle originates from a sinewy and quite wide beginning in the hipbone where the main muscles that flex the femur are twisted downward. Ascending obliquely from here and becoming fleshy first in the lumbar region, it is inserted into all the acute vertebral processes on its side and ends at the upper extremity of its insertion into the vertebra situated immediately beneath the vertebra which is supported at both ends. At its lower extreme it does not descend the same distance in dogs as in apes, since it is inserted in more lumbar vertebrae in monkeys than in dogs. This is because more lumbar vertebrae of monkeys have this process, which is always more prominent and extends farther from the vertebrae, the closer these vertebrae are to the vertebra which is supported at both ends, and the stronger the insertion the muscle we are talking about makes into them. As a result the thoracic vertebrae as well that are situated below the vertebra which is supported at both ends — in those animals generally the tenth — have this process just as do the upper lumbar vertebrae. Those closest to the sacrum, also not fully receiving an insertion of this muscle, lack the process. This had been observed by Galen 22 when he wrote that this process became known to him first, 23 and when elsewhere he boasts that muscles situated in the loins and serving there the motions of the spine had been wrongly understood by the ancients: everywhere propounding his apes to us where he pursues some subject or another with greater care and, as it were, zeal.

There are fewer 24 than five vertebrae in the loins of apes and dogs
But all the apes I have dissected so far, especially those which were caudate, and dogs as well, had more than five vertebrae in their loins; nor do I know whether there happen to be found other kinds of ape which have just five vertebrae in their loins like humans, having a shorter trunk than the apes we have. Yet Galen everywhere counts only five, 25 nevertheless accommodating the rest of his account to apes (as we have just shown) rather than man. It is possible that because the number had been set by all the ancients together, he agreed and handed on to posterity fewer vertebrae than were presented to him in apes. Perhaps in humans he found in the country or at least, as is likely, in skeletons not brought home he saw a number of specimens with five, while in the rest of the frame and in his fuller account of the bones he persuaded himself (as he often did elsewhere) that human vertebrae were similar and equal to simian without considering the matter more carefully.

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]