POSITION IX THE THORAX. 315 



their cartilages ; 1, placed on the lower part of the manubrium of the sternum, and on the 

 place of the arch of the aorta indicated by dotted lines ; 2, placed in the second left in- 

 tercostal space, on the stem of the pulmonary artery ; 3, apex of the right auricle ; 3', 

 its most prominent part, behind the third space ; 3", its lower part at the junction of the 

 sixth and seventh right costal cartilages with the sternum ; 4, left auricular appendix ; 

 5, 5, right ventricle ; 6, left ventricle ; 6', apex of the heart : the white line outside the 

 heart is intended to indicate the external pericardium, as if the anterior half were re- 

 moved by a transverse incision; 7, 7, vena cava superior; 8, 8, internal jugular veins ; 

 9, 9, subclavian veins, joining the jugular ; 9, 7, 9, innominate veins ; the right rising 

 behind the sterno-clavicular articulation, the left crossing obliquely behind the upper 

 half of the manubrium. The position of the first parts of the innominate artery, left 

 carotid and left subclavian arteries, is indicated behind and below this vein ; 9', 9', outer 

 part of the subclavian arteries. It is to be observed that in this figure the attachment 

 of the sixth costal cartilage to the sternum is represented a little too high. 



The auriculo-ventricular openings lie in the line of the auriculo-ventri- 

 cular sulcus. The middle of that of the right side lies behind the sternum, 

 between the fourth costal cartilages, and extends to the fifth left costal 

 cartilage. The middle of the left auriculo-ventricular opening is in the 

 second intercostal space, less than an inch to the left of the sternum ; but 

 as it is placed deeply, and overlaid by the arterial openings, the part imme- 

 diately over it is unfavourable for auscultation, which is therefore best 

 conducted at the point of impulse. The orifice of the pulmonary artery, 

 according to Luschka, is placed immediately to the left of the sternum, 

 opposite the second intercostal space, the free margin of the anterior valve 

 reaching up to the lower border of the second rib. The aortic orifice, 

 behind the insertion of the third left costal cartilage and the sternum, is on 

 a slightly lower level than the orifice of the pulmonary artery, and is 

 covered by it in two-thirds of its breadth. The aortic orifice being thus 

 concealed, the sounds produced within it are best heard at the spot where 

 the aorta approaches nearest to the surface, viz., opposite to the first and 

 second intercostal spaces at the right margin of the sternum. (Luschka, 

 Die Brustorgane, 1857 ; and Anatomie des Menschen, &c., 1863 ; Walshe, 

 Diseases of the Heart and Great Vessels ; Sibson, On the Normal and 

 Abnormal Situation and Structure of the Viscera of the Chest, in Trans, of 

 the Proviuc. Med. and Surg. Assoc. , vol. xii., year 1842, and in his Work 

 on Medical Anatomy ; Allen Thomson, Notice of the case of E. Groux, &c., 

 with Observations on the Position and Actions of the Heart, in Glasgow 

 Med. Journ. April, 1858.) 



The following additional particulars are taken from the observations of Allen 

 Thomson. The summit of the aortic arch is on a level with the middle of the 

 manubrium sterni ; and the left border of the innominate artery at its origin from the 

 arch is slightly to the left side of the middle line. The middle of the commencement 

 of the aorta, where it springs from the left ventricle, is behind the left border of the 

 sternum, on a level with the lower edge of the third costal cartilage. The ascending 

 part of the aorta bulges beyond the right border of the sternum to the extent of at 

 least a quarter of an inch ; and the vena cava superior extends about half an inch 

 farther in the same direction. The trunk of the pulmonary artery is wholly to the 

 left of the middle line, and its left border is about three-quarters of an inch beyond 

 the left border of the sternum. The concavity of the aortic arch is on a level with the 

 junction of the manubrium with the body of the sternum. 



The right auricular appendage covers the lower part of the ascending aorta to the 

 right of the pulmonary semilunar valves, and its point is exactly behind the middle 

 line on a level with the upper border of the third costal cartilages. 



The most projecting part of the right ventricle with the conus arteriosus lies 

 behind the sternum, between the lower end of the body and the inner part of the 

 left third intercostal space. 



The right auricle extends to fully an inch beyond the right border of the sternum. 



Y 2 



