IlEPTILES. 



as far as the i'econd vertebra, where it is infertcd. This 

 alfo 13 one of the retraftors ot the head. There are very 

 diltinft iiiter-artieiilarcs, vvhieh by their adlioii elevate eaeh 

 of the vertebrx, and coiifequently extend the neck. The 

 tranfverfo-fpinuhs is lituated on the polterior part of tlie 

 neck : it arifes from all the fuperior tranlverfe procelles, 

 and is inferted into all the fpinous procedes as far as the 

 fixth. Finally, a fliort mutcle proceeds from the upper 

 part of the full dorfal vertebra below the fliell, and is in- 

 ferted into the articular procefTes of the fixtli and leventh 

 cervical vertebra. This niulcle is peculiar to the tortoife, 

 and begins the extenfion of the neck wlien the head in con- 

 cealed within tlie fhell. 



Mufcles of the Ribs, Abdomen, ISjc. — In the frog, which 

 wants ribs, and the tortoile, where they are immoveable, the 

 mufcles which ulually have their infertions in them, are in 

 thole animals extended to other parts. Thus in the tor- 

 toife, whofe breall -plate occupies the place of the abdo- 

 minal mufcles, they are inlerted into the pelvis, wliich they 

 move. With relpefl to thofe animals, one very remark- 

 able obfervation may, in general, be made. It appears 

 that the very lingular fliape of the mulcles and bones depend 

 upon each other. Indeed, as the mulcles are not placed 

 upon the bones, they have not, if we may be allowed the 

 expreffion, fafhioned them ; and the want of motion in the 

 bones, which has given an unnatural figure to the trunk, 

 has alfo given to the mufcles other forms and other ufes. 

 The abdominal mufcles of the frog prefent nothing peculiar, 

 except that the ikin does not adhere to their furfaces, 

 and that inllead of being inferted into the ribs, they are 

 fattened to the Iternum by a Itrong aponeurofis. The 

 fame obfervations may be made with refpeft to the fala- 

 manders. 



We have defcribed, in tlie ofleology, the adaptation of 

 the ribs of ferpents to the purpole of progreflive motion ; 

 and now proceed to point out the mufcles by which 

 they are moved forwards or backwards, and connefted to 

 the abdominal fcuta. The ribs are brought forwards by 

 five fets of mufcles placed on the outfide of the cheil, and 

 pafling obliquely from above, downwards, outwards, and 

 backwards. I. One from the tranfverfe procefs of each 

 vertebra to the rib behind it. 2. The next fet arifes 

 from the ribs, at a fliort diltance from the fpine, palles over 

 two ribs, fending a flip to each, and ends in the third. 

 The third arifes from the pofterior edge of each rib, pafl'es 

 over two ribs, and is inferted into the third rib behind it. 

 The fourth fet palfes over one rib and is inferted in the 

 fecond. The fifth goes from rib to rib. 



The mufcles carrying the ribs backwards are found on 

 the infide of the cheR, and llant from the fpine forwards 

 and outwards. A ftrong fet arifes from the anterior fur- 

 face of the vertebra, goes over four ribs, to be inferted 

 into the fifth about its middle. The ferrated portions of a 

 ftrong flat mufcle, forming the mufcular covering of the 

 abdomen, arife from this part (the middle of the internal 

 furface) of each rib. The right and left mufcles unite in 

 a beautiful middle tendon. Thus it is obvious, that the 

 inferior half of each rib (below the origin of the fer- 

 rated portion jull defcribed) is external to the abdominal 

 mufcle, and confequently free for the purpole of progref- 

 five motion. 



The ends of the ribs are connefted to the abdominal 

 fcuta by a fet of lliort mufcles : they are alio connefted 

 together by (hort and Itraight mufcles. Another fet goes 

 from the heads of the ribs obliquely backwards to be fixed 

 in the fl<in at the edge of each fcutum. See fir E. 

 Hume's paper quoted in the olteology ; and particularly 



plates 4 and 5 from Mr. Clift's drawings, in which the 

 parts are reprefented. 



There is a comijlicatcd mufcular apparatus for extending 

 and retrafting tlie ribs, and carrying the fl<in forwards and 

 backwards in tlie cobra de capello. The ribs are raifcd or 

 carried forwards by four fets of mufcles, all arifing from and 

 inferted in thefe bones, and diredled obliquely from above, 

 downwards and outwards. 



The fliin of the back is brought forwards On the neck 

 by a large fet of very long mnfcles, arifing fucceflively 

 from each of the firtt twenty ribs, by a tendon, which 

 fooii becomes flelliy. The longell is about two inches. 

 They go backwards to he inferted into the (kin, which 

 they can bring forwards to a great extent when the ribs 

 have been firll extended. 



The mufcles which carry the ribs back again lie on the 

 infide of the cheft under the fj)iiie. One fet goes from 

 the vertebrae of the neck to the lower edges of the ribs : 

 but they pafs obliquely upwards and outwards over three 

 ribs, to be inferted into the fourth, thus acquiring a length 

 of fibre, by which the range of motion produced is much 

 increafed. The fecond fet goes from the ends of the ribs 

 forwards to the Ikin, whicli they will draw back. The 

 third fet from the root of one fcutum to the fcutum immedi- 

 ately above it, fo as to bring it down upon the other. 

 Sir E. Hume's and Dr. Ruliel's paper, and particularly 

 the engravings from Mr. Clift's drawings. Phil. Tranf. 

 1804, pt. 2. 



Mufcles of the Head. — The mufcles of the head of the 

 tortoife cannot be defcribed under names fimilar to thofe of 

 mammiferous animals and birds, becaufe the ihell aftbrds in- 

 fertion to the greater number of them. We will, therefore, 

 only diilinguifh them by the points of attachment. Thus, on 

 viewing the back part of the neck, we remark, lit, at the 

 anterior part of the back-ftiell, near the angle of the lunula, 

 a broad mufcle, which extends to the lateral and pofterior 

 parts of the head, into which it is inferted. It pulls the 

 head backward. 2. Beneath, and from the middle of the 

 anterior lunula of the back-(liell, there arifes another mufcle, 

 which is thin and round, and wliich, in fcparating from that 

 of the oppofite fide, forms an angle like the letter V : it is 

 inferted on the outfide of the preceding mufcle, and has the 

 fame ufe. 3. A mufcle analogous to the fplenius capitis 

 rifes from the fpinous procefi'es of the fourth and fifth cer- 

 vical vertebrae, by diftintt flips, and is inferted into the occi- 

 pital arch. Its ufe is to raife the head. 4. A mufcle 

 analogous to the reftus major anticus rifes from the infe- 

 rior tubercles of the four vertebrae next to the atlas, and is 

 inferted, fleiby and thick, into the deprellion of the cunei- 

 form procefs below the condyle. 5. The trachelo-maftoi- 

 deus rifes from the interior tubercles of the fecond and third 

 cervical vertebra;, by two thin aponeurotic tendons; it is in- 

 ferted, by a very thick and entirely flefliy portion, into the 

 protnberance that anfwers to the mattoid procefs. Its ufe 

 is to bend the head laterally. 6. Laftly, at the fuperior 

 part of the cervical fpine there is a fliort mufcle, which pro- 

 ceeds from the inferior part of the foramen, fonned by the 

 temporal folTa, and is inferted into the fpinous proceffes of 

 the firft, fecond, and third vertebra of the neck. On 

 viewing the neck in front, we obferve the mufcle analogous 

 to the iterno-cleido-maftoideus attached to the ftrong aponeu- 

 rofes that furround the humerus at its articulation with the 

 i'capula. The lower part of it, for one-third of its length, 

 can only be feen, the remainder being concealed by a mufcle 

 compofed of tranfverfe fibres, which fupplies the place of 

 the mylo-hyoideus, and platiima-myoides. It is infertcd 

 into a procefs correfponding to the malloid. Its ufe is to 



draw 



