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Part T. A N A 1 O M Y. i69 And we may fay in general, that the upper vertebra The tranfverfe procefTes of the dorfal vertebras are long, thicker at their ends than in the middle, and turn- of the back lofe gradually their refemblance to thofe of the neck, and the lower ones come nearer to the figure ed obliquely backwards. The fpinal procefi'es are long, fmall pointed, and Ho- of the lumbar. ping downwards and backwards; from their upper and The lowed: order of the true vertebra is the lumbar, back-part a ridge rifes, which is received by a fmall which are five bones, that may be diftinguiftied from any channel in the fore-part of the fpinal procefs immediate- others by thele marks: i. Their bodies, though eft" a ly above, which is here connected to it by a ligament. circular form at their fore-part, are fbmewhat oblong The conduit of the fpinal marrow is here more circu- from one fide to the other; which may be occafioned by lar, but, correfponding to the fize of that cord, is fmall- the prefiure of the large veflels, the aorta and cava, and er than in any of the other vertebrae, and a larger (hare of the vifeera. The epiphyfes on their edges are larger, of the holes in the bony bridges, for the tranfinilTion of and therefore the upper and lower furfaces of their bothe nerves, is formed in the vertebra above, than in the dies are more concave than in the vertebra of the back, one below. 2. The cartilages between thefe vertebra are much the The connexion of the dorfal vertebrae to the ribs, the thickeft of any, and render the fpine convex within the thinnefs of their cartilages, the eredt fituation of the o- abdomen, by their greateit thicknefs being at-their foreblique procelfes, thelength, Hoping, and connection of the part. 3. The oblique procefles are ftrong and deep; fpinal procefles, all contribute to 'refrain thefe vertebrae thofe in oppofite fides being almoft placed in parallel from much motion, which might difturb the actions of planes; the fuperior, which are concave, facing inthe heart and lungsand, in confequence of the little wards, and the convex inferior ones facing outwards: motion allowed here, the intervertebral cartilages fooner and therefore each of thefe vertebra receives the one a(hrivel, by becoming more folid: And therefore, the ffrft bove it, and is received by the one below ; which is not remarkable curvature of the fpine obferved, as people fo evident in the other two dalles already deferibed. advance to old age, is in the lead Hretched vertebrae of the 4. Their tranfverfe procefles are fmall, long, and alback ; or old people firft become round-fliouldered. * moft ered, for allowing large motion to each bone, and The bodies of the four uppermoft dorfal vertebrae de- fufficient infertion to mufcles, and for fupporting and deviate from the rule of the vertebrae, becoming larger as fending the internal parts. 5. Betwixt the roots of the they defcend; for the firfl of the four is the largeft, and fuperior oblique and tranfverfe procefies, a fmall protuthe other three below gradually become fmaller, to allow berance may be obferved, where fome of the mufcles the trachea and large veflels to divide at fmaller angles. that raife the trunk of the body are inferted. 6. Their The two uppermoft vertebrae of the .back, inftead of fpinal procefies are ftrong, ftreight, and horizontal, with being very prominent forwards, are flatted by the adtion broad flat fides, and a narrow edge above and below; of the mufculi longi colli and redti majores. this laft being deprefl'ed on each fide by mufcles. And The proportional fize of the two little depreffions in at the root of thefe edges, we fee rough furfaces for fixthe body of each vertebra, for receiving the heads of ing the ligaments. 7. The canal for the numerous the ribs, feems to vary in the following manner ; the de- cords, called cauda equina, into which the fpinal marpreHion on the upper edge of each vertebra decreafes as row divides, is rather larger in thefe bones than what far down as the fourth, and after that increafes. contains that marrow in the vertebrse of the back. The tranfverfe proceHes are longer in each lower ver- 8. The holes for the paflage of the nerves are more etebra to the feventh or eighth, with their fmorith fur- qually formed out of both the contiguous vertebra than faces, for the tubercles of the ribs, facing gradually in the other clafles; the upper one furniflies however the more downwards; but afterwards, as they defcend, they larger (hare of each hole. become (hotter, and the fmooth furfaces are diredted more The thick cartilages between thefe lumbar vertebra, upwards. their deep oblique procefles, and their ereft fpinal proThe fpinous procefles of the vertebrae of the back be? cefles, are all (it for allowing large motion; though it come gradually longer and more Hunting from the firft, is not fo great'as what is performed in the neck; which as far down as the eighth or ninth vertebra; from which appears from comparing the arches which the head dethey manifeftly turn fhorter and more eredt. feribes when moving on the neck, or the loins only. The firft vertebra, befides an oblong hollow in its low- The lumbar vertebra, as they defcend, have their ober edge, that alfifts in forming the cavity wherein the fe- lique procefles at a greater diftance from each other, tyid cond rtb is received, has the whole cavity for the head facing more backwards and forwards. of the firft rib fonp£d in it/ Both tranfverfe. and fpinal procefles of the middlemoll The fecond has the name "of axillary, without any vertebrse of the loins are longeft and thickeft; in the verthing particular in its ftrudture. tebra above and below they are lefs: fo that thefe proThe eleventh often has the whole cavity for the ele- cefles of the firil and fifth are the lead, to prevent their venth ri£> in its body, and wants the fmooth furface on ftriking on the ribs or ofl'a ilium, or their bruifing the each tranfverfe procefs. mufcles in the motions of the fpine. The twelfth always receives the whole head of the laft The ephiphyfes round the edges of the bodies of the rib, and has no fmooth furface on its tranfverfe procefles, lumbar vertebra are moft raifed in the two loweft, which which are very (hort. The fmooth furfaces of its inmake them appear hollower in the middle ferior oblique procefles face outwards as the lumbar do. confequently than the others are. Vql. I. No. 8. Uu The 3
