THE EIGHT AURICLE. 



2it 



oralis or isthmus Vieussenii, whilst the floor of the fossa, formed by what 

 was previously a valve, is thin and translucent ; and occasionally 

 a small oblique passage leading into the left auricle is left between it 

 and the annular border. At the right part of the cavity are seen the 

 orifices of the superior and inferior cavte ; the former passing down- 



Fig. 1G7.— The Right 

 Auricle a.vd Ven- 

 tkicle opened and a 



PART OF THEIR RiGHT 



AND Anterior Walls 



REMOVED SO AS TO SHOW 

 THEIR INTERIOR (Allen 



Thomson). One-halp 

 THE Natural Size. 



], the superior vena 

 cava ; 2, the inferior vena 

 cava at the place where it 

 passes through the dia- 

 phragm ; 2', the hepa- 

 tic veins cut short ; 3, 

 placed upon the tubercle 

 of Lower within the cavity 

 of the right auricle ; -j, 

 placed in the fossa ovalis, 

 the Eustachian valve is 

 just below ; 3", is placed 

 close to the aperture of 

 the great coronary vein 

 and its valve ; + , + , 

 the auriculo - ventricular 

 groove, a narrow piortion 

 of the adjacent walls of 

 the auricle and ventricle 

 having been preserved ; 

 4, i, on the right side of 

 the septum, the cavity of 

 the right ventricle ; 4', 

 large anterior columua 

 carnea ; 5, the anterior ; 

 5', the inferior, and 5", 

 the septal segment of 

 the tricuspid valve ; 6, 



is placed in the interior of the pulmonary artery, a part of the anterior wall of that 

 vessel having Ijeen removed, and a narrow poi-tion of it preserved at its commencement 

 where the pulmonary valve is attached. The valve is represented half-closed ; two of the 

 segments are seen foreshortened, the third sideways ; 7, concavity of the aortic arch close 

 to the cord of the ductus arteriosus ; 8, ascending part or sinus of the arch covered at its 

 commencement Viy the auricular appendix and pulmonary artery ; 9, placed between the 

 innominate and left common carotid arteries ; 10, appendix of the left auricle ; 11, 11, 

 the outside of the left ventricle, the lower figure near the apex. 



wards and forwards, the latter, the larger, being directed upwards and 

 inwards. Between the two orifices is a slight projection, better marked 

 in_ certain quadrupeds than in man, which has received the somewhat 

 misleading name of tuber cJe of Lower (fig. 167, 3). 



In front of the orifice of the inferior cava, and partly covering it, is a 

 crescentic fold of the lining membrane, the Eustachian valve. This is 

 continuous by its convexity with the margin of the venous orifice, and its 

 antei-ior cornu is prolonged into tlie anterior limb of the annulus 

 ovalis. This valve, which is very variable in character in the adult, being 



