Marriner. — On the Anatomy of Hyla aurea. 263 



Arterial System of Hyla Aurea. 

 The truncus arteriosus (fig. 4, t.) comes from the ventricle 

 of the heart and divides almost immediately into two main 

 branches. After running for a short distance each half divides 

 into three branches, known as the " aortic arches." (For the 

 sake of simplification, one side only — namely, the left side — will 

 be described.) 



A. Carotid Arch (fig. 4, i). — This is the upper of the three 

 arches, and after running for a short distance it divides into two 

 branches — viz., the lingual artery (fig. 4, I.), which comes off 

 just in front of a swelling in the carotid, known as the " carotid 

 gland," and runs forward along the muscles of the lower jaw 

 towards the snout, breaking up into smaller branches as it pro- 

 ceeds; and the carotid artery (fig. 4, c), which runs round the 

 oesophagus, then, after bending backwards so as to overlap the 

 systemic arch, runs forwards and downwards and enters the skull 

 a little to the left of the median line. I have not been able to 

 make out very clearly the course of the carotid artery after it 

 enters the head, but it appears to divide up into internal and 

 external carotids. 



B. Systemic Arch (fig. 4, ii). — This is the middle of the three 

 arches, and runs round and down over the oesophagus to the 

 dorsal body-wall. It then continues on as a large artery and 

 joins with its fellow on the other side, just anterior to the 

 kidneys, to form the dorsal aorta. When opposite the arm this 

 arch gives off two arteries, viz. : — 



(a.) The occipito-vertebral (fig. 4, oc.) : This is seen as a very 

 short, thick artery running downwards and forwards, and dis- 

 appears into the muscles of the dorsal body-wall. In Rana 

 this divides into two branches — namely, the occipital and the 

 vertebral — but in Hyla I have only been able to make out the 

 occipital (fig. 4, oc), which runs up to the muscles on the side 

 of the head and also to the orbit. 



(o.) The subclavian artery (fig. 4, s.) branches off from the 

 systemic arch near the origin of the occipital vertebral. It runs 

 out as a large artery to supply the arm. 



C. Pulmo '-cutaneous Arch (fig. 4, in). — This is the third of 

 the aortic arches, and just before it reaches the lung it divides 

 into two, viz. : — 



(a.) The cutaneous artery (fig. 4, cu.) runs outwards and 

 downwards, and disappears in the muscles at the angle of the 

 jaws. It can be traced to the dorsal surface, where it runs as 

 a large vein along the skin from the pectoral down to the pelvic- 

 girdle. It has a number of small branches which supply the 

 skin. 



