REPTILES. 



tnont ; it pallos under the ham, auJ in infortcd into the tibia, 

 which it bends. That which is analogous to the fai-torius 

 arifcs from tlie 03 pubis, near the interofleous hgament, and 

 paffes over the knee, to be iniertcd into the tibia, wiiicfi it 

 extends. A mufclc com])ofed of two flefliy portions, both 

 of which aril'e from the lateral parts of the facrum, is in- 

 ferted below the head of the tibia, and bends the leg. In 

 its aftion, it much refcmbles the biceps, from whicli, how- 

 ever, it differs with refpecl to its attachments. Another 

 nnifcle, refembling the fafcia lata, and very thin in its flcfliy 

 part, arifes from the fidea of the coccyx. It paffes under 

 the il<in of the fin, to its infertion, almoff oppofite to the 

 heel. It bends the leg upon the thigh, and extends the foot 

 upon the leg. The mufcle analogous to the biceps arifes 

 from the facrum and ilium. It goes to the external furface 

 of the leg, where it is inferted into the fibula. The cxten- 

 for of the leg prefents notliing particular. The mufcle ana- 

 logous to the red'tus anterior arifes from the internal furface 

 of the pubis, and joins the common tendons of the cx- 

 tenfors. 



Mufclesof the Ankle. — In tlie frog, the gaftrocnemius has 

 only one belly ; it has, however, a i'mall tendon, by which 

 it is inferted into the outward fide of the head of the tibia. 

 Its tendon runs under the heel, and there Aiding over a lefa- 

 moid bone, expands itfelf under the foot, to form the plan- 

 tar fafcia. There is neither folcus nor plantaris. The ti- 

 bialis anticus rifes' by a ftrong tendon from the lower part 

 of the OS femoris. About the middle of the tibia it divides 

 into two bellies, one internal, the other external. The ten- 

 don of the firlt is inferted into the tibial bafe of the long 

 bone of the tarfus, and that of the fecond into the fame bone, 

 a little more outwardly. An aflillant to this mufcle arifes 

 from the middle and anterior part of the tibia, and pro- 

 ceeds to the internal fide of the bafe of the long bone of the 

 tarfus. The tibialis poilicus relembles the human, but it is 

 only inferted into one bone of the tarfus, wr.. that which is 

 long, and fituatedat the inner fide. There is but one mufcle, 

 to which the term pcroneus can apply. It arifes by a flen- 

 der tendon, from the external condyle of the thigh, and is 

 inferted into the bafe of the tibia, on the outfidc, by two 

 tendinous portions, one of which extends to the bone of the 

 tarfus. It extends the leg with refpeft to the thigh, or, 

 more properly, the thigh with refpeft to the leg. Befides 

 thefe mufcles, which extend from the leg to the foot, there 

 is another which arifes from the metatarfal extremity of the 

 tibia, at its internal edge, paffes between the two bellies of 

 the tibialis anticus, and proceeds very obliquely to its infer- 

 tion, at the digital extremity of the long bone of the tar- 

 fus, on its inner fide. In the fea tortoife, the mufcles of the 

 feet are fupplied by aponeurotic fibres, fomewhat fleffiy, 

 which ferve only to llrengthen the articulations, and keep 

 the fins properly extended. 



Mufcles of the Toes. — There is no extenfor longus digi- 

 torum in the frog ; neither is there any flexor propnus 

 poUicis. The extenfor brevis digitorum is very dillinft, it 

 arifes from the whole length of the long external bone of the 

 tarfus, and extends obliquely to all the four toes, the lall 

 excepted. It is inferted into the lail phalanges. There 

 are fuperior and inferior interoll'eous mufcles, which are 

 very apparent, to the number of ten. Their direftion is 

 very oblique. The flexor communis digitorum is fituated 

 under the long bone of the tarfus, on the inner fide, and is 

 covered by the aponeurofis of the gaftrocnemius. When 

 it reaches the little bones of the tarfus it divides into five 

 tendons, which receive, at their inner fide, affiftant flefhy 

 fibres, apparently proceeding from a mufcle fituated below 

 the long bone of the tarfus, on the inner fide. It may per- 



haps reprefent the flexor longus. In the fea tortoife all 

 thefe mufcles have their places fupplied by bundles of 

 aponeurotic fibres. 



On the Support of the Body, and its Motions in Progrejfwn. 

 — Standing is an attitude common to all animals, but thtf 

 circumilances attending it diflcr very confidcrably. In moll 

 of the oviparous quadrupeds, the knees and elbows are 

 direftcd outwards as they ftand, and even during their 

 various progreffivc motions. The pofterior members, arti- 

 culated more in proportion at the fides of the body, are fo 

 bent, that the belly defcends to the ground, and moves 

 along it. 



Turtles reft on their plaltron, and on their four flattened, 

 elongated, and fin-hke members. They may be compared 

 to feals in their mode of executing movements. They 

 employ their members, either in (wimming, or in walking 

 on the fea-fliore, or in digging holes in the fand to receive 

 their eggs. 



In tortoifes, fl;anding is nearly the fame as molt in othcj" 

 oviparous quadrupeds ; and the direftion of their body is 

 horizontal. Batracians, and frogs in particular, generally 

 have their body, when at reft, in an oblique elevation ; the 

 arms fuftaining the front part, while the back remains on 

 the ground. The formation of the pofterior limbs does not 

 render them adapted to raife the body in a vertical diredtion, 

 but merely to pufli it forwards. 



Serpents, in a ftate of repofe, coil up their body in 

 feveral circles, either rifing one above the other, or ar- 

 ranged one within the other ; and the head is elevated above 

 this coil. Thofe which inhabit trees are twifted round 

 the branches. The chalcides and biped lizards may be 

 compared to ferpents when at reft, for they are coiled up, 

 and their limbs ferve merely to prevent the body from 

 rolling. 



Walking exhibits different modifications, according to 

 the number and form of the limbs, and the relative fize of 

 the fore and hind-feet. Where they are of equal length, 

 the animals move with great velocity : hence the names of 

 certain fpecies, as lacerta agihs and velox. When, however, 

 the limbs are too fmall and weak for the body, the move- 

 ments are flower, as in the crocodile, the chalcides, and the 

 toad. 



The feet of tlie cameleon, and its prehenfile tail, make it 

 a better climber than moll reptiles. 



The limbs being all of nearly equal length in the fcinks, 

 they cannot leap well : while the iguanas and tupinam- 

 bes exhibit confiderable agility. The frogs are the great 

 jumpers, from the great length and ftrength of the hind 

 limbs. But they can hardly walk ; moving the front legs 

 only with facility, and being obliged almoft to drag the hint! 

 ones after them. 



Serpents can leap or project their bodies by the fudden 

 extenfion of feveral articulations : they form feveral curves 

 with their body, and then fuddenly llraighten them, either 

 in whole or in part, according to the leap which they may 

 wifli to make. 



Creeping, properly fo called, belongs only to ferpents, 

 and confifts of a projeftion of the body backwards or for- 

 wards, produced by the alternate motion of one or feveral 

 of the lower parts agamft the ground. The following 

 modifications are exhibited in different inftances. i. Creep, 

 ing by vertical undulations. 2. By horizontal undulations. 

 3. By two or three undulations of the pofterior third part of 

 the body, while the two anterior thirds are elevated verti- 

 cally. 4. A Aiding kind of crawling, by fmall undula- 

 tions formed by the alternate approximation and repara- 

 tion of rows of fcales placed tranfverfely under the body. 



5. The 



