237 



A round red organ, in the mesentery near the beginning 

 of the rectum, is the spleen. 



Describe (1) the Venous System, (2) the Arterial System, and 

 (3) the Heart of the Frog. 



(1) The impure blood is collected into three principal 

 veins (right and left superior venae cavae and inferior vena 

 cava), which open into the sinui venosus. Each anterior 

 or superior vena cava is formed from the union of external 

 jugular (formed by union of the lingual and the mandibular 

 veins), innominate (formed by internal jugular and sub- 

 scapular), and subclavian (formed by brachial and musculo- 

 cutaneous). The posterior or inferior vena cava is formed 

 between the kidneys from renal veins, and it receives the 

 genital and the hepatic veins. 



Each femoral vein (of the leg), divides into two branches, 

 a femoro-abdominal or pelvic and a femoro-renal, which 

 receives the sciatic (back of the thigh) and becomes the 

 renal portal, which enters the kidney. The two ' pel vies 

 join to form the median anterior abdominal* ; it receives 

 the hepatic portal* vein from the gut and spleen, and, 

 dividing into two, enters the lobes of the liver. There is 

 a renal portal and a hepatic portal system (vessels marked *). 



The pulmonary veins, which return the blood (purified) 

 from the lungs, join before entering the left auricle. 



(2) From the short ventral aorta ("truncus"), and at 

 each side, three arterial arches arise, namely, the carotid, 

 the systemic, and the pulmo -cutaneous. The carotid gives 

 off the lingual artery (to tongue) and the carotid artery (to 

 buccal cavity, orbit, and brain). The two systemic arches 

 unite in front of the kidneys to form the dorsal aorta, which 

 gives off (at its formation) a coeliaco-mesenteric artery to 

 liver and gut and spleen, and renals, genitals, and an 

 inferior mesenteric to the rectum. Finally the aorta bi- 

 furcates into two iliacs, which supply the pelvic region 

 and legs. One of the arteries given off by each systemic 

 arch (before union) passes to the shoulder (subclavian) and 

 thence into the arm (brachial). The pulmo-cutaneous 

 divides into the cutaneous (to skin) and the pulmonary, 

 which conveys the impure blood to the lungs. 



(3) The heart is enclosed in a thin membrane, the peri- 

 cardium, and consists of a sinus venosus opening into the 

 right auricle, a left auricle, and a conical thick-walled 

 ventricle with a thick- walled conus.jp|The auriculo-ventricu- 

 lar opening is guarded by valves, and^three pocket or semi- 



