Elements of biology; a practical Elements of biology; a practical text-book correlating botany, zoology, and human physiology elementsofbiolog00hunt Year: [c1907] CIRCULATION 351 In the frog some of these blood vessels are somewhat difficult to find; otners may easily be seen. One which collects blood from the skin and muscles near the ventral surface of the body, but chiefly from the hind legs, is called the abdominal vein. It may be seen near the surface, on the ventral midline of the body, as we open the frog from the ventral side. This vein turns inward at a point nearly between the fore
Elements of biology; a practical Elements of biology; a practical text-book correlating botany, zoology, and human physiology elementsofbiolog00hunt Year: [c1907] CIRCULATION 351 In the frog some of these blood vessels are somewhat difficult to find; otners may easily be seen. One which collects blood from the skin and muscles near the ventral surface of the body, but chiefly from the hind legs, is called the abdominal vein. It may be seen near the surface, on the ventral midline of the body, as we open the frog from the ventral side. This vein turns inward at a point nearly between the fore limbs, divides into two branches, and enters the liver. Just before it reaches the liver, another vein, bringing blood from the digestive tract, joins with it. The rest of the blood from the hind legs has to pass through what is known as the renal portal system of circulation, the veins of which send the blood through the kidney, and thence, by a large single vein (the postcaval vein) to a thin-walled sac on the dorsal side of the heart. This sac, known as the sinus venosus, receives the blood from the veins and emp- ties it into the heart. Immediately before reaching the sinus, the blood from the liver (the so-called portal circulation) joins with the postcaval vein. It is seen in the portal circulation that part of the blood of the body passes through the liver before reaching the heart. Blood from the head region is returned to the heart by two large precaval veins. The blood from the fore limbs also takes this course. ^2cV.' Venous system of the frog; , abdominal vein; , femoral vein; H, heart; L, lungs; K, kidney; LIV., liver; , pul- monary vein; Pr. , pre- caval vein; R., R., renal veins; SV, sinus venosus; , sci- atic veins. (After Parker and Haswell.) Circulation of the Blood in Man. — As in the frog and other vertebrate animals, the organs of circulation are the heart and blood vessels. These blood vessels are called arteries when they carr
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