ilEPTlLP:S. 



has alfo thefe three boiios, wliicli unite to form tlic glenoid 

 cavity, and corrcipoiid witii tin; icapiih, fork, and clavicle. 

 But as their refpcftivc difpofition is very remarkable, il ap- 

 pears neceflary to give a particular defcriptiuu of them. 

 One of the bones extends from the bafe of the rudiment of 

 the firll rib, to which it is iixed by a ligament, as high as 

 the humeral cavity, where it is intimately counettcd with 

 the other two. The fecond bone may be confidered as the 

 continuation of the tiril, which it joins at the humeral 

 cavity, of whicii it forms part. Its other extremity is at. 

 tached to the breaft-plate, and ilrong ligaments likewife 

 uuite the extremity to that of the poilerior bone. Thefe 

 two bones, thus united, are flightly bent outwards, fo as 

 to leave between them and tliofe of the oppcfite fide, an 

 oval fpace, through which the oefophagus, the trachea, and 

 feveral mufcles, pafs. The firll feems to corj'efpoud to the 

 clavicle, and the iecond to the os furciforme. Finally, the 

 third bone of the flioulder is fituated below tlie abdominal 

 and thoracic vifcera, nearer the breall-plate. It is long, 

 and extends from the humeral cavity, of which it forms the 

 lower part, as far as the abdomen. It feems to fupply the 

 place of the fcapula by the number of mufcles infcrted into 

 it, but its fituation is jull the reverfe of that bone. A very 

 ftrong hgament unites this bone to the fecond. 



Bone of the Ann. — The humerus of the tortoife has a 

 very remarkable (liape. As in birds it is articulated at 

 once to the fcapula, clavicle, and os furciftn-me, by a large 

 oval head, the grcatelt diameter of which lies m the direftion 

 of the flatneli of the bone. A coniiderable eminence rifes 

 above this large head, which, by its curvature and its ufes, 

 lias fome relation to the olecranon, a procels which, in this 

 animal, the bone of the iore-arm wants. Below the head 

 there is another eminence, lefs projecting, but more rough, 

 which likewife ferves as a point of iniertion to fome 

 mufcles, and fupplies tlie place of the little tuberofity. The 

 reft of the body of the bone is flattened and narrow towards 

 the middle. In the crocodile, the humerus is roimd, but a 

 little bent like an S in its wliole length. At the extremity 

 that joins the fcapula, it refembles the tibia ; its head, inllead 

 of being round, is fiat ; and its tuberolity, which is fmgle, 

 is anteriorly in the form of a ridge, and lomewhat inclined 

 inwards. In the other lizards, and in frogs, the humerus 

 exhibits nothing peculiar. Serpents having no limbs, have 

 confequently no humerus. 



Bones of the Fore-arm. — The humerus of the crocodile 

 terminates in two round tubercles. The hollow head of the 

 radius turns upon the external one. Between them the 

 round head of the ulna is fituated, but it has neither ole- 

 cranon nor figmoid cavity. In the upper part it is the 

 largeft of the two bones, but the fmallelt below. There is 

 nearly the fame conformation in the cameleon, but the bones 

 are more elongated, and the inferior head of the radius is 

 lefs than that of the ulna. In the frog the fmgle bone of 

 the fore-arm is articulated by a concave head, with a large 

 round tuberolity on the bafe of the humerus, between its 

 two condyles. On each lide, where the lower part of this 

 bone becomes larger, we obferve r. furrow, which is the 

 only veftige of a diftindlion into two bones. Troja has 

 pointed out a lingularity in the ilruAure of the bone of the 

 fore-arm and of the leg in frogs and toads. Thefe bones 

 confift of a fingle piece, which is folid in the middle, but 

 divided at either extremity into two conical portions, having 

 manifeft medullary cavities. See Memoria fopra la ilruttura 

 fingolare della tibia e del cubito nelle Rane e nci Rofpi, in 

 his Sperienze intorno alia Rigenerazione delle OITa. Nap. 

 I779> P-2SO, t. 7, 8. 

 The two bones of the fore-arm of falamandcrs arc fituated 



one above the other. The ulna, which is the low .-ft, and 

 fomewhat longell of the two, has no olecranon ; but there 

 is a fort of rotula in the tendon of the extenfor mufclej. 

 The ulnar extremity of the humerus is much enlarged. The 

 articulate lurface which terminates it isconven, and permit! 

 the radius and ulna to turn together in every diroftion. 

 The two bones of the fore-arm in the turtle are always in a 

 forced ilitc of pronation. The radius, which is much 

 longer than the ulna, and fixed to it by a cartilaginous fub- 

 flance, is the lowed, and extends even under the carpus. 

 Thefe two bones much refemble each other in the humeral 

 extremity, being formed by a fingle concave furface re- 

 ceived upon a correfpondent pulley of the humerus. Their 

 articulation is fuch that it allows them to move together 

 laterally, and a little upward and downward in the aftion of 

 fwimming. 



Boms of the Hand. — The frog, the toad, the falamander, 

 have three ranges in the carpus. The firll confills of two 

 bones, one radial and one ulnar ; the fecond confills of 

 three bones, the largell of which bears the rudiment of a 

 thumb with two joints ; the third range has likewife three 

 bones. The fecond fingers proceed from the firll of thefe 

 bones ; the fourth finger is articulated with the fecond 

 bone ; the middle finger articulates with both bones ; the 

 little finger joins the third bone. The firft range touches 

 the third infcrioriy, becaufe the fecond is cuneiform. There 

 is no bone without the range. In the mud tortoife, the firll 

 range is a fingle bone, whicli feparates the radius from the 

 ulna : the fecond range confills of two bones, and a fmall one 

 out of the row, fituated on the ulnar edge ; the third range 

 confills of five bones, one for each bone of the metacarpus. 

 The fea tortoife has three bones in the firll range, the 

 ulnar bone being the longell. The two anterior bones do not 

 advance much farther. The third range confills only of 

 three bones for thofe of the metacarpus, and one fmall bone 

 out of the row, fituated upon the radial fide. 



In the crocodile, the firll range confifts of two long 

 parallel bones. It has befides two little external bones 

 without the range on the radial fide. The number of the 

 phalanges varies in thefe animals. The crocodile has the 

 hand rounded. It has two phalanges to the thumb, three to 

 the fecond finger, four to the middle and fourth fingers, and 

 only three to the little fingers. 



The cameleon has three fingers on one fide, and two on 

 the other, which form, with the three oppofite to them, a 

 kind of forceps. The number of the phalanges is the fame 

 as in the crocodile, with the exception of the little finger, 

 which has four. In the falamander the little finger is obli- 

 terated, and the thumb has only two phalanges. 



The frog has only one phalanx to the thumb. The two 

 following fingers have only two phalanges. The other two 

 fingers have three. 



The hand of the fea tortoife is long, and compreffed in 

 the form of a fin ; there are two phalanges to the thumb, 

 three to the three fucceeding tots, and two only to the laft. 

 A fimilar conformation is obfervable in the mud tortoife ; 

 with this exception, that its hand is rounded. 



Bones of the Pel-u'is. — In the turtle, that part of the os 

 innominatum which correfponds to the pubis, is the moil 

 confiderable. It proceeds from the cotyloid cavity by a 

 thick portion, which comes forwards and widens into a thin 

 flat lamina, divided into two parts ; one is turned towards 

 the middle line, by which the two correfponding bones are 

 united ; the other is free, and is dirccled to the external 

 fide. The portion which correfponds with the ilium is 

 Ihort, narrow, and thick ; it rells on the ihell, and is joined 

 to the facruin ; finally, the portion which is analogous to 

 ? D 2 the 



