. A manual of zoology for the use of students : with a general introduction on the principles of zoology . Zoology. 432 MANUAL OF ZOOLOGY. between the ventricles a perfect one, and even in these, as in all other Reptiles, the heart consists functionally of no more than three chambers. The ordinary course of the circulation, where the ventricular septum is imperfect, is as follows :—The* impure venous blood returned from the body is, of course, poured by the vense cavae into the right auricle (fig. 163, a), and thence into the ventricle. The pure arterialised and aerated blood that has passed t
. A manual of zoology for the use of students : with a general introduction on the principles of zoology . Zoology. 432 MANUAL OF ZOOLOGY. between the ventricles a perfect one, and even in these, as in all other Reptiles, the heart consists functionally of no more than three chambers. The ordinary course of the circulation, where the ventricular septum is imperfect, is as follows :—The* impure venous blood returned from the body is, of course, poured by the vense cavae into the right auricle (fig. 163, a), and thence into the ventricle. The pure arterialised and aerated blood that has passed through the lungs, is, equally of course, poured into the left auricle {a'), and thence propelled into the ventricle (w). As the ventricular cavity is single, and not divided by a complete partition, it fol- lows of necessity that there is a mixture in the ventricle, resulting in the production of a mixed fluid, consisting partly of venous and partly of arterial blood. This mixed fluid, then, occupies the common ventricular cavity, and by this it is driven both to the lungs (through the pulmonary artery), and to the body (through the systemic aorta). Conse- ^ quently, in Reptiles, both the . lungs and the various tissues and. Fig. 163.—Diagram of the circulation in Reptiles. (The venous system is left light, the arterial system is black, and the vessels containing mixed blood are f,^"vf„'o'utVio:d''J?o'ntb=idT:t; organs °f .the body are supplied Left auricle, receiving arterial blood With a miXtUre of arterial and from the lungs : z* Arterio-venous ven- „-,„„.,„ ui ] _J ._ tricle, containing mixed blood, which is VCnOUS DlOOQ, and nOt With Un- driven by W the pulmonary artery to mixed blood the lunffS with the lungs, and by (0) the aorta to the , , , , °, body. purely venous, and the body with purely arterial blood—as is the case with the higher Vertebrata. In the Crocodilia, as before said, the partition between the ventricles is a complete one, and c
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