. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. 330 AVES. distinct cavities, wluch have the same relations to each other, and impress the same course on the circulating fluid.* The form of this viscus is always that of a cone, sometimes wide and short, as in the Ostrich and Crane; sometimes more elongated, as in the Emeu (Jig- 167) and Vulture; or still more acute, as in the Curlew, Common Fowl, &c. Its situation is more anterior and mesial than in Mammalia, and its axis is always parallel with the axis of the trunk. It is not contained with the lungs in an especi
. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. 330 AVES. distinct cavities, wluch have the same relations to each other, and impress the same course on the circulating fluid.* The form of this viscus is always that of a cone, sometimes wide and short, as in the Ostrich and Crane; sometimes more elongated, as in the Emeu (Jig- 167) and Vulture; or still more acute, as in the Curlew, Common Fowl, &c. Its situation is more anterior and mesial than in Mammalia, and its axis is always parallel with the axis of the trunk. It is not contained with the lungs in an especial cavity, but its apex is lodged between the lobes of the liver; the diaphragm not being so far developed as to separate the chest from the abdomen. As the lungs are confined to the dorsal part of the chest, the whole of the anterior surface of the pericardium is exposed when the sternum of the bird is removed. The pericardium is thin, but of a firm texture, and adheres by its ex- ternal surface to the surrounding air-cells. It is of considerable size, and commonly prolonged for some way between the lobes of the liver. The auricles of the heart in Birds have not externally such distinct appendices as in Mam- mals. The right auricle is much larger than the left; it is more distinctly divided internally into a sinus (d, fg. 167) and auricle proper Fig. Heart of the Emeu, than in Mammals, and these parts are separated by a more complete valvular structure; in which respect Birds bear a closer analogy to Reptiles. Three veins terminate in the sinus, there being in Birds always two superior cava?, as in Reptiles. The right superior cava («), which returns the blood from the right wing and right side of the neck, terminates in the upper and anterior part of the sinus; the left superior cava (b, b) winds round the pos- terior part of the left auricle to open into the * The blood of Birds differs from that of the other Vertebrate classes in the greater number of globules, and
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