. An analytical compendium of the various branches of medical science, for the use and examination of students. Anatomy; Physiology; Surgery; Obstetrics; Medicine; Materia Medica. DEVELOPMENT OF THE FCETUS. 45 collected by the vena cava descendens, and emptied also into the right auricle, from whence it passes into the right ventricle^ from thence mainly- through the ductus arteriosus into the aorta, a small portion only passing into the pulmo- nary artery. From this it will be seen that the liver is the only organ that receives the blood from the placenta unmixed. Every other organ receiving
. An analytical compendium of the various branches of medical science, for the use and examination of students. Anatomy; Physiology; Surgery; Obstetrics; Medicine; Materia Medica. DEVELOPMENT OF THE FCETUS. 45 collected by the vena cava descendens, and emptied also into the right auricle, from whence it passes into the right ventricle^ from thence mainly- through the ductus arteriosus into the aorta, a small portion only passing into the pulmo- nary artery. From this it will be seen that the liver is the only organ that receives the blood from the placenta unmixed. Every other organ receiving mixed arterial and venous. After Urth, the current is entirely changed by the esta- blishment of respiration, and its diversion into the lungs. The ductus venosus, and the ductus arteriosus shrivel up into ligamentous cords; the foramen ovale shortly closes by the apposition of its valve ; the pulmonary artery and vein become dilated to receive the increased current, and the circulation, which before re- sembled that of the higher reptiles, becomes now that of the perfect mammal. It not unfrequently happens, how- ever, that some arrest of de- velopment takes place, and prevents the completion of these changes ; * The fcelal circulation ; 1, the umbilical cord, consisting of the umbilical vein and two umbilical arteries; proceeding from the placenta (2); 3, the umbilical vein dividing into three branches ; two (4, 4) to be distributed to the liver; and one (5) the ductus venosus, which enters the inferior vena cava (6); 7, the portal vein, returning the blood from the in- testines, and uniting with the right hepatic branch ; 8, the right auricle ; the course of the blood is denoted by the arrow, proceeding from 8 to 9, the left auricle; JO, the left ventricle; the blood following the arrow to the arch of the aorta (11), to be distributed through the branches given off by the arch to the head and upper extremities. The arrows, 12 and 13, represent the return of the blood from the
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