276 



which has yet to be determined. The heart of the adult frog has fewer 

 capillaries than the fish heart. 



Hyutl^) described the heart of frogs as an organ without blood 

 vessels, the sinusoids not being considered vessels, and the coronary 

 capillaries being confined to the epicardium. In the frog the single 

 coronary artery arises from the carotid subdivision of the right truncus 

 aortae, just beyond its bifurcation, and descends over the bulbus, forming 

 capillaries. These are gathered into the coronary vein, found on the 

 posterior side of the base of the ventricle where it receives a few 

 branches from the epicardium in its immediate vicinity. The vein then 

 becomes detached from the ventricle and crosses the pericardial cavity, 

 sheathed in epicardium, to enter the abdominal vein. Thus the auricles, 

 except at the auriculo - ventricular groove, and most of the ventricles 

 (the lower three-fourths, Martin) are without capillaries, even in the 

 epicardium. 



Martin^), by injecting the ventricle of the frog's heart, discovered 

 what he considered to be the true coronary artery, issuing directly 

 from the ventricle to supply its upper fourth and the bulbus arteriosus. 

 Banchi ^), who could not find this vessel in toads, believes that, through 

 partial injection, Martin mistook a superficial portion of the sinu- 

 soidal sponge for an artery. In his own injections Banchi noticed such 

 appearances. Until it has been found that anastomoses between the 

 capillaries and sinusoids do not occur in frogs, as they do in certain 

 fishes, it must be considered possible that Martin, through such a 

 connection, injected a part of the coronary system. 



The heart of an adult turtle, Chrysemys picta, is supplied by a 

 single coronary artery which arises from the right truncus aortae and 

 descends the bulbus, after dividing into two branches. These extend 

 over the dorsal and ventral sides of the ventricles respectively, giving 

 rise to numerous capillaries. The returning vein ascends the ventral 

 side of the ventricle, passes under the auricles to its dorsal side and 

 descends, partly in company with the dorsal artery to enter the right 

 wing of the venous sinus. All the large coronary branches are found 

 in the epicardium. They supply a thin compact superficial layer of 

 ventricular muscles with vessels, as described by Hyrtl, but leave the 



1) J. Hyrtl, Vorläufige Anzeige über gefäßlose Herzen. Sitz.-Ber. 

 d. Akad. d. Wiss. Wien, Bd. 33, 1858, p. 573. 



2) Martin, 1. c. p. 44 seq. 



3) A. Banchi, Morfologia delle arteriae coronariae cordis. Arch. Ital, 

 di Anat. e di Embryol., Vol. 3, 1904, p. 146. 



