REPTILES. 



five firll dorfal vertebrae have a lateral tubercle for the liead 

 of the rib, and another on the tranfverfe proccis for its tu- 

 bercle : thus tlie rib is articulated only to one vertebra. 

 But tlie firft of thefe articular furfaces is wanting in the re- 

 maining ribs, while each of their tranfverfe procefles has 

 two articular faces. Tlie fame number (feven) is found in 

 moil lizards, though the cameleon has only two. The fa- 

 cral vertebra; are very few in every fpecies, and none of them 

 have a large os lacrum. 



As frogs have no ribs, no diftinftion can be formed with 

 refpeft to the three firft orders of vertebrae in them. They 

 have in general eight between the neck and the pelvis, all 

 furnilhed with pretty long tranfverfe proceHes. The laft 

 are the longeit, and touch the ofi'a ilii. In the toads, the 

 tranfverfe procefles are very large, and fhaped like hatchet 

 blades. The os facrum confifts of a fingle bone only : it is 

 long, pointed, comprell'ed, and has no coccyx. In the 

 pipa, which has the tranfverfe procefles of the fecond and 

 third vertebras much longer than the others and almoft like 

 ribs, this bone is ofiified with the laft vertebrse. 



The falamanders have fourteen vertebrs between the head 

 and the facrum ; they have all nearly the fame fliape, ex- 

 cept the firft, which receives the head, and the laft, which 

 is articulated to the facrum. The two extremes of the 

 fpine alone want the veftiges of the ribs, which confift of 

 fmall oblong moveable bones, aftually articulated to the 

 tranfverfe procefles, which here take a pofterior direftion. 

 The articular procefles are large, and wedged together. 

 The pofterior rell upon the anterior, fo as to impede the 

 motion of the fpine backward. The facrum confifts only 

 of a fingle vertebra, but there are twenty-feven in the tail. 



In ferpents, the vertebrae alone conftitute almoft the 

 •whole (keleton. It appears in general, fays Blumenbach, 

 that the number of vertebrae, in red-blooded animals, is in 

 an inverfe proportion with the fize and ftrength of their ex- 

 ternal organs of motion. Serpents, therefore, which en- 

 tirely want thefe organs, have the moft numerous vertebrae ; 

 fometimes more than three hundred. (Comp. Anat. p. 1 18.) 

 In confirmation of this remark, we may obferve how nu- 

 merous the vertebrae are in the elongated fifties, as the eel, 

 and in the whales, as the porpoife, (above one hundred in 

 the former, and between fixty and feventy in the latter). 

 Birds, whofe wings give them fuch vaft power of locomo. 

 tion, have very few vertebrx, if we confider the anchylofed 

 ones as forming a fingle piece ; and the frog, with its im- 

 menfe hind extremities, has a very ftiort fpine, confifting of 

 Itill fewer pieces than that of birds. The vertebra: of this 

 order are nearly of the fame form, from the head to the tail : 

 the body, as well as the fpinous, articular, and tranfverfe 

 proceries, are eafily diftinguiftied. In certain kinds, for 

 inilance the boae, the fpinous procefles, which are continued 

 throughout the whole length of the back, are feparated 

 from each other, and allow reciprocally a motion fufSciently 

 confpicuous. Wherever this difpofition of the fpinous pro. 

 ceffes prevails, the body of the vertebrae, on the fide next 

 the belly, prefents only an obfcure projefting line. In 

 other kinds of ferpents, as for example the rattlefnake, the 

 fpinous procefles are long, and fo large as to touch each 

 other. They have, for their bafis, the articular procefles, 

 which lie on each other like tiles. In confequence of this 

 ftrufture, the motion of the fpine towards the back is very 

 circumfcribed, but its motion towards the belly and fides 

 much augmented. The bodies of the vertebra play very 

 eafily in thefe direftions upon one another, and are armed 

 with a fliarp fpine tending towards the tail, which only ob- 

 ftrufts their motion when it might produce a luxation. 

 Thfs firft vertebra differ from thofe of the reft of the body, 



only in having the rudiments of the ribs much fmaller : 

 there is no neck in thefe animals. The vertebrae of the tail 

 diff'cr no farther than in having no ribs, and that their fpines, 

 both ventral and dorfal, are double, or form two ranges of 

 tubercles. The articulation of the bodies of the vertebrae 

 with each other is very remarkable : the anterior part of 

 the body of the vertebra prefents a frnooth hemifpherical 

 tubercle, and the pofterior part a correfponding cavity ; fo 

 that each vertebra becomes connefted to thofe next it by a 

 fort of knee-joint. This mode of articulation fully explains 

 the motion of reptiles, which is performed winding from 

 fide to fide, and not up and down, as it is reprefented 

 by painters. 



Table of the Number of the Vertebrae in Reptiles. 

 I. Oviparous Quadrupeds. 



II. Serpents. 



Of ike Ribs and Steynum. — The thorax of reptiles is very 

 various in its ftrufture. Frogs have a fternum, but no ribs; 

 ferpents have ribs, but no fternum ; tortoifes have the ribs 

 oflified to the back.ftiell, and the fternum included in the 

 breaft-plate ; the crocodile and lizard have perfecl ribs, but 

 their fternum is almoft entirely cartilaginous. In the cro- 

 codile, the firft portion of the fternum is oflified and elon- 

 gated. It receives the two clavicles. The remaining part 

 is entirely cartilaginous. It is united with the os pubis, 

 and fends off" eight cylindrical cartilages fo the parietes of 

 the abdomen. This llrudlure, conftituting a fpecies of ab- 

 dominal fternum, apparently for fupporting the vifcera, is 

 quite peculiar to the crocodile. The ribs are twelve in 

 number, the two firft and two laft of which are not attached 

 to the fternum. The intermediate ribs have upon their pof- 

 terior edges cartilages partly oflified, which fupply the place 

 of the angles of the ribs in birds. All the pofterior ribs, 

 beginning at the fifth, are only articulated to the tranfverfe 

 procefles of the vertebrae, which are of great length. The 

 five firft articulate with the vertebrae at two points, one on 



its 



