REPTILES- 



additional (Irengtli, but greatly diminifhing the cavity of 

 the ventricle. Thefe fafciculi are mollly I'eparate from each 

 other, allowing the blood to permeate between them as 

 through a fieve ; thus effecling the more perfect admixture 

 between the portion arriving from the lungs and that from 

 the body. The openmgs of the auricles are found clofe to 

 each other, at the middle of tlie bafe of the heart, above 

 the feptum. Each orifice is clofed by a femicircular valve 

 of a membranous ttrudture, the loofe edge of which corre- 

 fponds to the auricle of the fame fide. The termination of 

 the arteries is found in the right fide of the bafe of the 

 organ ; that belonging to the pulmonary artery is fituate 

 towards the left and in the lower part, correfponding to 

 the inferior cavity. On the left of the latter is found the 

 opening of the left aorta, correfponding to the fame cavity, 

 and placed oppofite to the opening which forms the com- 

 munication between the fuperior and inferior cavity. The 

 opening of the right aorta is found immediately behind the 

 laft, and correfponds more particularly to the fuperior 

 cavity, in which is received both the blood from the lungs 

 and that from the body ; the two portions united are pro- 

 jected partly into the right aorta and partly into the in- 

 ferior cavity, and from thence into the left aorta and 

 pulmonary artery. 



In the fourth order of reptiles, the batracians, the heart 

 prefents a ftrufture the leaft complicated of the whole clafs. 

 It confiits of a fiiiglc auricle of a rounded figure, broader 

 than the bafe of the organ, with its parietes ftrengthened 

 by flelhy fafciculi. At the bafe of the auricle is the orifice 

 of communication with the ventricle, which is fingle, having 

 a fimple cavity, with fleftiy columns, not feparated from 

 each other. At its bafe is found the common trunk of the 

 arteries, arifing by a fingle orifice, fituate more to the right 

 and lovi'er down in the ventricles than the opening of the 

 auricles. The heart of the frog has been delineated by 

 Swammerdam, Bibl. Natur. tab. 49; and by Roefel, Hiftor. 

 Ranar. 



Of the Blood-Vejfds. —The diftribution of the blood-veffels 

 in the four orders of reptiles is varied according to the ftruc- 

 ture of the heart, and many other circumftances in their 

 organization. In the batracians the arrangement differs in 

 the greatefl degree from that of mammalia and birds. All 

 the arteries arife by a fingle trunk ; confequently there is 

 but one opening in the heart. In the three other orders, 

 there are at leatl two openings, frequently three, which 

 give origin to as many diflintl trunks, one of which is 

 deflined exclufively to the lungs. 



Of the Arteries in the Che/oiiians. — The arteries of tlie 

 body arife from the heart by a fingle or double trunk in 

 different fpecies ; thofe of the lungs by a fingle trunk. 

 They are firmly connedtcd together for a Ihort dif'cance from 

 their origin. The trunk of the pulmonary artery arifes on 

 the left, lower down than that of the body. It quickly 

 feparates into two branches, one of which proceeding to the 

 right lung, turns from the left to the right, then advances 

 forwards to arrive at the anterior part of the organ, where 

 the infertion of the bronchus takes place. The other pro- 

 ceeds in a contrary dircftion, paiTing acrofs the cefophagus, 

 it arrives at the fummit of the left lung. 



The trunk of the arteries of the body takes its origin at 

 the right extremity of the bafe of the heart, and divides al- 

 moft immediately into two great branches, tlie right and 

 left pofterior aortae. When the trunk is double at its ori- 

 gin, they feparate, forming thefe two branches. The right 

 aorta furniflies, near its origin, another confiderable artery, 

 which may be denominated the anterior aorta. This foon 

 divides into two branches, each of which is again fubdivided 



into two others, tlie internal of which, the fmalleft, is flic- 

 common carotid, and the external, the fubclavian or axillary 

 artery. The common carotid proceeds by the fide of the 

 neck, concealed by the mufcles going to the on hyoides, 

 fending branches to the cefophagus and adjacent mufcles. 

 It arrives at the head, to the parts of which it is ultimately 

 diltributed, without dividing prcvioufly into two principal 

 branches analogous to the carotids of mammalia. The fub- 

 clavian or axillary artery furiiilhes nearly the fame branche; 

 as the arteries bearing the fame name in mammalia, with 

 the exception that tliere is no branch correfponding to 

 the inferior thyroid. The continuation of the trunk, form^ 

 the brachial artery. The two pofterior aorta; proceed on 

 each fide upwards and outwards ; then bending backwards, 

 they approximate again, and are connetled by a communi- 

 cating branch, which the left aorta gives to the right ; nearly 

 oppofite to the fifth dorfal vertebra. 



The right aorta, previoufly to communicating with the 

 left, furniflies many arteries to the back or upper fhell, 

 correfponding to the intercoftals. The left aorta furiiifhes 

 confiderable arteries to the vifcera of the abdomen, which 

 confume great part of its blood. When the trunk arrives 

 beyond the cardia, it divides into three branches ; the firft, 

 which is the fmalleft, furniihes a branch to the cefophagus, 

 and then is diftributcd to tlie flon-.ach. It is analogous to 

 the coronary ftomachic of manimaha. The fecond, almoft 

 as confiderable as the trunk from which it proceeds, diitri- 

 butes arteries to the intcilines, fpleen, pancreas, and liver, 

 in the following manner. ' The hepatic artery is the firft 

 given off on the right fide ; it turns backwards and down- 

 wards to arrive at the liver, and divides into two branches, 

 near the bafe of the vifcus, from one of which proceeds a 

 fmall branch to the pancreas, and numerous others to the 

 duodenum. The fecond branch is one of fniall fize, and is 

 diftributed to the fecond turn which the colon makes to the 

 right. It is the colica dextra. The third branch paffes 

 from the right to the left, and diftributes its branches to 

 the tranfverfe colon. It is the colica media. After having 

 given off thefe branches, the trunk purfues a fhort courfe 

 between the layers of the peritoneum, in a direction down- 

 wards and backwards. It then dillributes the following 

 . branches. The pancreatic, which paffes from behind for- 

 wards upon the left border of the pancreas. The fplenic, 

 a very fmall artery, diftributed exclufively to the fpleen. 

 A very confiderable branch, belonging to all the right part 

 of the colon and cacum. It is a fecond colica dextra. A 

 fmall artery, which, after having gi\'en a branch to the 

 caecum, proceeds to anaftomofe with the next, the proper 

 mefenteric artery, which is larger than any of the preced- 

 ing, and ramifies in the mefenfery of the fmall mteftine, to 

 which it is ultimately diftributed. Laftly, tlie third branch, 

 refulting from the divifion of the pofterior left aorta, the 

 fecond in magnitude, proceeds obliquely to the right and 

 backwards, and anaftomofing, as has been mentioned, with 

 the right aorta, without furnifhing any branch. The com- 

 mon trunk, formed by their union, appears rather as a con- 

 tinuation of the right aorta ; it extends along the vertebral 

 column to thx? pelvis, giving off the following branches in 

 its courfe. Five or iix fmail branches on each fide, corre- 

 fponding to the intercoftal or lumbar arteries. The fper- 

 matics. One or two branches on each fide to the kidnies. 

 A fmall artery correfponding to the pofterior mefenteric, 

 which is diftributed to the cloaca. 



The common pofterior aortic trunk terminates by four 

 branches, in the individuals belonging to the teftudo graeca, 

 which we have diffetted. The firft on the left was the ex- 

 ternal ihac of that fide, then came the internal iliac of the 



fame 



