Markiner. — On the Anatomy of Hyla aurea. 259 



2. The cutaneous veins (c.) are a pair of medium-sized vessels 

 bringing blood from the skin for a short distance posterior to 

 the arms. Each vein is composed of a number of small branches, 

 which arise from the skin ; they unite and form the large vessel 

 which, after running for a short distance across the ventral 

 body-wall, disappears just below the pectoral girdle. 



3. The parietal veins (p.) are a pair of veins often as large 

 as the cutaneous, and they bring blood from the skin about half- 

 way down the abdomen. They, like the cutaneous veins, are 

 much branched, and the main trunk runs across the ventral 

 body-wall and soon disappears into the body-cavity. Their 

 course as they run to meet the anterior abdominal vein can 

 often be traced through the body- wall. 



4. The pelvico-cutaneous veins {p.c.) are a pair of veins bring- 

 ing blood in from the skin.around the pelvic girdle. Each vein 

 is composed of several branches, and these uniting run through 

 the body-wall near the junction of the legs to the trunk. If 

 the body-wall be opened it will be seen that they connect with 

 the renal portal veins just after the bifurcation of the femoral 

 veins. Near the mid- ventral line and just anterior to the 

 pelvic girdle there are often_ one or two very small, short veins 

 running out to the skin. 



Venous System Proper. 



If the ventral body-wall be cut up a little to one side of the 

 middle line, and the flaps laid back after the anterior abdominal 

 vein has been dissected off, the following veins can be seen. 

 Pin the heart back so that the ventricle is pointing towards the 

 snout. 



The sinus venosus (fig. 2, s.v.) is a thin-walled sac lying on 

 the dorsal wall of the heart. It is more or less triangular in shape, 

 and is made up by the union of the posterior vena cava, which 

 enters it from the lower end, and the right and left venae cavee, 

 which enter it from the right and left corners respectively. 



Veins opening into the Sinus Venosus. 



I. Left Anterior Vena Cava (fig. 1, v.c.). 



This is a large, short vein opening into the sinus venosus 

 at its left side, and returns blood from the left side of the head 

 and left fore-limb. It is made up by the union of three veins — 

 namely, the external jugular, the innominate, and subclavian — 

 about 5 mm. from the heart, whence it runs upwards and in- 

 wards to the sinus venosus. 



Veins that unite to form the Left Anterior Vena Cava. 

 1. External Jugular Vein (figs. 2 and 3, e.j. ; and fig. 1, e.j.). — 

 This is by far the largest and most important vein of the three, 



