REPTILES. 215 



Formerly it was supposed that the batrachians have only a 

 single auricle of the heart. Later investigations, however, first by 

 J. Davy, and afterwards the nearly contemporaneous observations 

 of other anatomists, have proved that the auricle of frogs is divided 

 internally by a partition, and thus is really double\ In the sala- 

 manders also and Prote'idce there is a similar partition, which, how- 

 ever, in some is incomplete or perforate^. The pulmonary veins 

 empty themselves in all these animals not, as earlier writers on com- 

 parative anatomy state (who usually gave merely an extract from 

 the description of the circulation in the frog offered by Swammerdam 

 more than a century and a half previously), into the anterior cavse, 

 but into the left auricle either separately and close together, or 

 (in frogs) after they have formed a short common stem. The 

 ventricle in these naked reptiles is single. It has a muscular 

 appendage {bulhus m-teriosus) at the origin of the arteries, which 

 corresponds to the appendage of the heart in cartilaginous fishes, 

 and in the Proteids, as well as in these, is provided with diiferent 

 rows of valves 3. In the serpents the ventricle is of a conical 

 form and divided by an imperfect muscular septum into two 

 chambers. From one of the cavities the pulmonary artery arises, 

 and from the other, or uppermost, towards the right side, two 

 arterial stems. The one of these large arterial stems, which runs 

 forward and to the right, gives off the arteries of the anterior part 

 of the body (two stems, the cephalic artery or common carotid, and 

 the arteria collaris, which CuviEK names vertebral artery). This 

 artery afterwards bends downwards to the right and gives off 

 some other branches, when it unites with the second large artery, 

 which on the left side of the heart, after having formed an arch, 

 runs backwards, and conveys blood to the parts only which are 

 situated behind the heart. Since the serpents have no limbs, they 

 have no subclavian arteries as distinct stems. Two descendino- vence 



^ Davy made the discovery in 1825, in toads; see Edhiburgh new Philos. Journal, 

 Vol. IX. pp. 160, 161. In 1832 two independent observers, Martin Saint- Ange and 

 M. .T. Weber, arrived at the same result. See M. J. Weber Beitrage zur Anat. und 

 Physiol. I. Bonn, 1832, 4to, s. i — 5, Tab. I. figs. 1 — 6. 



^ Owen, Transact, of the Zool. Sac. 1835, i. pp. 213 — 220, PI. 31. According to 

 Hyetl, the septum in Proteus is incomplete. 



^ See the figure of the heart of Menopoma in the Catalogue of the physiol. series of 

 comp, Anat. in the Museum of the Coll. of Surgeons, 11. 1834, PI. xxiii. fig. 2. 



