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**Article Three**
Concerning the Thoracic Vertebrae.
Know, esteemed one, that anatomists have stated: The thoracic vertebrae are those attached to the ribs and containing, preserving, the vital organs within. They are twelve in number; eleven of them possess both spinal and transverse processes, while one lacks a transverse process. Their bodies are not equal in size, for the one closest to the heart—the most important of the organs—is the largest and strongest. The transverse processes of these vertebrae are more robust than those of others, so that the ribs cannot reach them. The seven upper thoracic vertebrae have been found to possess large processes and thick, strong transverse processes, in order that they may safeguard the heart, the ruler of the organs, with utmost care. For the bodies of these vertebrae are directed towards their spinal and transverse processes. Their articular processes have been found to be short and broad. The articulations on the upper side of the vertebra above the tenth vertebra [117/a] contain sockets. And the tubercles belonging to the projections below enter those sockets, inclining the bodies downwards. The spinal process of the tenth vertebra is depressed like a dome. The two sockets on either side of the articular processes are socketless, for they have been joined from beneath. The sockets of the lower part of the tenth vertebra incline towards its upper side, and their cavities incline towards its lower side; their bodies incline upwards. The twelfth vertebra lacks a transverse process, as it does not require one since it has a rib attached to it. The tip of the peritoneum is attached to the twelfth vertebra. This vertebra’s upper part is very small, so it is independent of needing many articular processes for stability. Because the thoracic vertebra is larger than the cervical vertebra, the vertebral foramina are not equally divided between the two vertebrae but gradually increase above and decrease below. The complete nerve aperture belongs entirely to the tenth vertebra. Since all the other vertebrae of the chest and all the vertebrae of the lumbar region, which lie between them and the thighs, completely encompass this aperture, cavities have been created on their right and left sides for the exit of the nerves. The vertebrae of the lumbar region possess a spinal process and broad transverse processes. Their articular processes are as wide as their lower portions and resemble protective projections. There are five bones in the lumbar region. Together with the sacrum bone, they form the base of the spine, being the support of the front of the column and the pubic bone, and the origin of the two sciatic nerves. The sacrum is composed of three parts, which are harder than all other vertebrae, their articulations more secure, and their wings wider. They have special apertures on their front and back sides for the nerves so that the hip joint may not obstruct them or crush them. The sacrum bone resembles the lumbar bones previously described. The coccyx is composed of three cartilaginous, soft vertebrae which lack extensions and projections. Being as small as the cervical vertebrae, the nerves emerge from the common foramina between the vertebrae; however, a single nerve emerges from the tip of the third vertebra.
From what has been reported thus far, it is understood that all parts of the spine are like a single entity. And the processes and other forms are circular in shape, for circular shapes are those least exposed to the dangers of collision and impact. Therefore, the upper vertebrae of the spine have their heads directed downwards, and the lower vertebrae have their heads directed upwards; and they are all gathered in the tenth vertebra, which is the middle one. The tenth vertebra is the center of the projections with respect to the length of the spine, and it is a convergence of two directions. Thus, the ninth vertebra, counted from each side, gathers upon the tenth vertebra, establishing order. Together with the cervical vertebrae, the total number of spinal vertebrae is twenty-six.
“We absolve the Wise Creator from all imperfection.”