. The biology of the frog. Frogs. 2S4 THE BIOLOGY OF THE FROG of the truncus is divided by two septa into three compart- ments. The anterior compartments, which lead to the com- mon carotid arteries, both enter the unpaired division of the truncus to the right of the septum. The middle com- partments, which lead to the aorta, open into the unpaired portion of the truncus on either side of the septum. The posterior compartments, which are continued into the pulmo-cutaneous arches, join each other and open by a common aperture into the bulbus cordis behind the valves at its anterior end. The Art
. The biology of the frog. Frogs. 2S4 THE BIOLOGY OF THE FROG of the truncus is divided by two septa into three compart- ments. The anterior compartments, which lead to the com- mon carotid arteries, both enter the unpaired division of the truncus to the right of the septum. The middle com- partments, which lead to the aorta, open into the unpaired portion of the truncus on either side of the septum. The posterior compartments, which are continued into the pulmo-cutaneous arches, join each other and open by a common aperture into the bulbus cordis behind the valves at its anterior end. The Arteries.—The arteries, or vessels which carry blood away from the heart, have thicker walls than the veins, and after death are usually almost devoid of blood. The ultimate ramifications of the arteries lead to a system of minute capillaries, through the very thin walls of which there is an exchange of products between the blood and the tissues. From the capillaries the blood flows into the veins, by which it is returned to the heart. All of the blood vessels with the exception of the capillaries are provided with coats of unstriated muscle, by the contraction and relaxation of which their caliber may be diminished or increased. The arterial system begins in the truncus arteriosus, which, after its bifurcation, splits up into three pairs of arteries which are symmetrically disposed on either side of the middle line. The anterior of these three arteries, the common carotid, soon divides into the lingual, or external carotid, and the larger internal carotid. The lingual runs forward, giving branches to the thyroid, pseudo-thyroid, various muscles of the hyoid apparatus, and tongue. At the junction of the internal and external carotid, but principally upon the former, there is an oval enlargement known as the carotid gland. Internally the carotid gland contains a spongy network which serves as an impediment to the flow of the blood. As this organ becomes somewhat distended. Please
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Keywords: ., bookauthorholmessamueljsamuelja, bookcentury1900, bookdecade1920
