SANGUIFEROUS SYSTEM. 48U 



at the base of the heart, as in other reptiles, although here 

 to a smaller extent and during a limited period of life. The 

 venous blood of the system received from the capacious right 

 auricle, appears to be transmitted to the inferior right cavity 

 of the ventricle, which gives origin to the left aortic trunk 

 and also to the common trunk of the pulmonary arteries. 

 These vessels are provided with semilunar valves at their 

 origins, and the pulmonary artery arises from a small fossa 

 of the right ventricle, a little distant from the origin of the 

 left aorta. The osseous lamina observed by Bojanus in the 

 heart of the tortoise, between the origins of the systemic 

 arteries, I have found in the same situation in the adult 

 gavial, where it formed an irregular tuberose morbid growth, 

 and measured about three quarters of an inch in length 

 and two lines in thickness. The arterialized blood from 

 the lungs, received by the small left auricle, and transmitted 

 to the superior, or left cavity of the ventricle, although 

 sparingly, and perhaps for a limited time, sent through 

 the opening of the septum, appears to pass chiefly into 

 the great bulbous trunk, which gives origin to the right arch 

 of the descending aorta, and to the right and left brachio-ce- 

 phalic arteries or arterise innominatse, which supply the ante- 

 rior parts of the body. Two semilunar valves are also placed 

 at the origin of this great right systemic artery, in the left di- 

 vision of the ventricle. The aerated blood is thus chiefly sent 

 to the head and arms, by the two ascending trunks from the 

 right aorta, which form the common carotid and the axillary 

 arteries of their respective sides, and also to the legs and tail 

 by the right aortal trunk. The right and left aortic arches, 

 proceeding from distinct orifices of the ventricle, unite to- 

 gether under the vertebral column, as in other reptiles, to 

 form the common trunk of the abdominal aorta, the right 

 arch of the aorta conveying arterialized blood principally to 

 the head, legs and tail, and the left aorta chiefly venous blood 

 to the abdominal viscera. 



All the three great trunks which originate from the 

 ventricles, the right and left aortse and the pulmonary 

 artery, form wide and elongated bulbous enlargements at 

 their commencement, and from this bulbous dilatation of 

 the right aorta arise the two large trunks, which soon 

 subdivide to form the common carotid and axillary or sub- 



