. The biology of the frog. Frogs. 266 THE BIOLOGY OF THE FROG ca The internal stru-cture of the heart presents a compHcated and beautifully adapted mechanism for propelling the blood always in one direction and keeping the pure and impure blood separated. By removing the ventral wall of the auricles, ventricles, and bulbus, most of the features of the internal structure may be exposed to view. The [i/iterauriailar septmh^ is so situated that the right auricle is much larger than the left. In the right auricle, close to the septum, is the large sinu-aiiricular aperture, through which blood
. The biology of the frog. Frogs. 266 THE BIOLOGY OF THE FROG ca The internal stru-cture of the heart presents a compHcated and beautifully adapted mechanism for propelling the blood always in one direction and keeping the pure and impure blood separated. By removing the ventral wall of the auricles, ventricles, and bulbus, most of the features of the internal structure may be exposed to view. The [i/iterauriailar septmh^ is so situated that the right auricle is much larger than the left. In the right auricle, close to the septum, is the large sinu-aiiricular aperture, through which blood en- ters from the sinus veno- sus. It is a transverse oval opening guarded by valvular lips on the ante- rior and posterior sides, which prevent the blood that has entered from the sinus from being forced back again when the auricles contract. The left auricle receives blood from the pulmonary vein through a small opening near the septum slightly anterior to the sinu-auricular aperture ; there is no valve at this point, but since the vein perforates the wall obhquely, the pressure caused by the contraction of the auricle serves to close the opening and thus prevents the backward flow of the blood. Both auricles empty into the ventricle by a large opening, the auriculo-ventricular aperture, which is. :xxir Fig. 73. — Heart seen from the dorsal side with the sinus venosus opened up. ao, aortic trunk; au, right auricle; au", left auricle; ca, carotid trunk; , pulmo-cutaneous trunk; //.f,precaval vein; , postcaval vein; , pul- monary vein; , sinus venosus; v, ventricle; va", sinu-auricular valves. (After Howes.). Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Holmes, Samuel J. (Samuel Jackson), 1868-1964. New York Macmillan
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectfrogs, bookyear1916
