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 16 On the Vertebrae of the Thorax

Variety based on the transverse processes

In the transverse


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processes (H and I in figures 1, 2, 3, 4), the thoracic vertebrae also vary from one to another, but not so much as Galen stated in the thirteenth book of De usu partium where he deprived the tenth vertebra and the two beneath it of transverse processes. 26 For there is a transverse process on each side of all vertebrae of the thorax; its size scarcely varies in the nine upper vertebrae, 27 while in the tenth the transverse processes swell out less than in the higher vertebrae, as the tenth rib attached to it is quite small and a false rib. The transverse processes of the eleventh vertebra are still smaller than in the tenth, and smaller yet in the twelfth, no doubt because the need for these processes is not so great as in the higher vertebrae. 28 All of these others have ribs articulated to them, for the sake of which the thoracic vertebrae have the strongest and thickest transverse processes. But ribs are not articulated to the transverse processes of the twelfth and eleventh vertebrae, for the two lowest ribs of each side are joined by a single articulation only to the body of the vertebrae, while the rest are jointed to the bodies of the vertebrae and the tips of the transverse processes. At the tips (K in fig. 1, and c, b in fig. 3, ch. 19) of the transverse processes of the upper nine thoracic vertebrae are seen depressions [fovea costalis processus transversi] coated with cartilage, to which the capitulum of the rib 29 (M in fig. 4, ch. 19) is articulated. In the transverse processes of the tenth vertebra, no such depressions are seen, or sometimes obscure ones, and in the processes of the lowest two none whatever occur. The depressions carved in the tips of the transverse processes are all located in the anterior portion, but some occupy the upper and others more the medial region. 30 The depressions of the transverse processes of the first vertebra face downward, of the ninth upward; of the middle, in between. Galen seems not to have noticed this: while explaining the rib joints, he judges that all such depressions face downward and are carved in the lower surface of the tip of the transverse process. 31 He should in no way have deprived the tenth thoracic vertebra and the two beneath it of their transverse processes on the grounds that they would inhibit the lateral motion of the entire backbone. 32 For if Nature had wished transverse processes to be absent from these vertebrae for the sake of that motion, she would not have had to deprive the vertebrae below the tenth (which Galen stated is supported above and below 33 ) of their transverse processes any more than those above. If the transverse processes of the lower vertebrae were to obstruct lateral motion, surely the upper ones would have resisted this motion no less than the lower. Just as the portion of the backbone below a vertebra that is received above and below is moved upward in that motion, so it is also necessary for the portion lying above it to be borne downward, if the backbone needs to be moved laterally as in a semicircle, where the midpoint of the semicircle’s circumference is rightly thought to be that vertebra which is supported above and below, whichever one that might be. But what is the use of lingering on this talk which is so difficult to understand because of the vertebra that is supported on both ends? The tenth and the two thoracic vertebrae below it have transverse processes as prominent as suits their function in the origin and insertion of muscles. Indeed Galen, who is to some degree consistent, stated in many places that all the ribs are articulated to two internodes, one in the body of the vertebra and the other on the transverse process. 34 If this were the case (which it assuredly is not), would not also the tenth thoracic vertebra and the two below it necessarily have transverse processes? We shall state in what direction the processes are extended, whether upward or downward, when we add the spines of the thoracic vertebrae to our account.



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 16 On the Vertebrae of the Thorax