201 
THe CrrounAtTion oF Mixep Bruoop In THE EmMBryo MaAm- 
MAL AND Brirp, AND IN THE ADULT ReEptine, Am- 
PHIBIAN AND F'lsuH. 
By A. G. POHLMAN. 
Our conception of the course of the blood through the heart of the 
lower vertebrates appears to be based almost entirely on the conditions 
found in the adult of the warm-blooded forms (birds and mammals). It 
is well known that the adult bird and mammal possess a double circula- 
tion, i. e., a cycle in which venous blood is propelled from the heart to be 
returned oxygenated (pulmonary circulation), and one in which arterial 
blood is expelled to be returned venous (systemic circulation). The 
afferent and efferent vessels are in no way connected save through a capil- 
lary system, and for this reason the heart may be divided into a right 
or venous and a left or arterial heart. While the greater part of the 
seventeenth century was occupied with the Harvey doctrine, the eighteenth 
century found men equally engaged with the course of the blood through 
the fetal heart. Three distinct theories were suggested before the begin- 
ning of the nineteenth century—one based on alleged physiological ne- 
cessity, a Second on the anatomical relations found in the fetal mammalian 
heart, and a third on the logical deductions from the differences between 
the fetal and adult circulatory conditions. The differences between the 
fetal and adult heart in mammals are, briefly, the right auricle receives 
the precavals (venous) and the post-caval vein (V. cava inf.), which ‘is 
arterial; a communication between the right and left auricle is present 
(foramen ovale), and a connection is found between the heart efferents 
(pulmonary artery and aorta) in the ductus arteriosus. 
The theory based on physiological necessity (von Haller-Sabatier) 
was this: if the left heart in the adult is arterial, then the chances are it 
must also be arterial in the fetus; hence the oxygenated blood in the post- 
caval vein must pass through the foramen ovale into the left heart. It 
was further inferred that because the ductus arteriosus short-cut the 
venous blood from the pulmonary artery into the descending aorta, the 
vessels arising from the aortic arch would convey a better quality of blood. 
