VOL. XXVII.] PHILOSOPHICAL TRANSACTIONS. 605 



to be inserted into the posterior part of the auricles. The right pulmonary 

 vein follows after the same manner the right axillary, which it quits after it 

 has entered the pericardium, to traverse almost all the length of the reserva- 

 tory, and meet the left pulmonary about two lines distance from the auricles. 

 These two veins thus united, open into the posterior part of the left auricle, 

 by a common oval orifice, furnished with two semilunar valves; by which 

 means they pour into this auricle all the blood that comes from the lungs 

 to the heart. 



By all that has been observed concerning the structure of the heart of 

 the land tortoise of America, and the disposition of both its auricles and 

 vessels, how extraordinary soever it may appear, it is impossible to find out 

 the least thing that may affect the opinion of Dr. Harvey, and all other 

 anatomists, about the manner of the blood circulating in the heart of a human 

 foetus, and the use of the valve at the foramen ovale; which is, to permit the 

 blood to pass from the right auricle through this hole into the left, and to 

 hinder the blood's passing from the left auricle by this hole into the right. 

 And 1 add further, that among all the known animals, we could not chuse one 

 whose heart may be more proper to confirm this opinion, than the land tortoise 

 of America, by reason of the simplicity of its structure, and of the plain and 

 distinct manner in which all the parts appear. 



Explication of the Figures. — Plate xvi. fig. 8, aaa represent the heart j bbb its auricles 3 c the 

 trunk of the pulmonary artery 5 d the arteria aorta descendens sinistra, e the superior aorta; h the 

 right descending aorta J v the ligament that suspends the cone of the heart in the pericardium j 

 GGGGG the pericardium laid open. 



Fig. 9, aaa represent the heart opened, to show the parts of its ventricles j b the double valve 

 covering the orifices of the ductus from the auricles j c the orifice of the right auricle i ; d that of 

 the left H J e the orifice of the pulmonary artery k ; f that of the left aorta L3 g the orifice common 

 to both the right aorta m, and the superior aorta n. 



Fig. 10, aaa represent the auricles j b the right auricle; c the left auricle; dd the muscular 

 septum, that divides the cavities of the auricles; e the orifice of the reservoir of the veins; f the 

 orifice of the pulmonary veins; gg the large parts of the funnels; h the muscular duct of the 

 funnels; ii the reservoir of the veins; k the left axillary vein; l the right axillary vein; m the 

 great intestinal vein ; n the great hepatic vein; 00 two small hepatic veins; p the right pulmonary 

 vein : q the left pulmonary vein. 



Fig. 11, a the heart of the tortoise ; b the trunk of the pulmonary artery; ccc &c. the branches of 

 the pulmonary artery, accompanying the bronchia in the lungs; dddd the left descending artery; 

 eeee the right descending artery ; ff a branch of the left aorta, which communicates with the right 

 aorta ; gg the intestinal artery ; h the superior or ascending aorta ; i the ligament that suspends the 

 heart ; k the trachea ; llll &c. the two branches of the trachea going to the lungs. 



