582 



HEART. 



Fantonus, that as three circular valves meeting 

 in the axis of a canal would leave a small space 

 in the axis itself, so the use of these corpora 

 Arantii may be to fill up the interval which 

 would thus otherwise be left, has generally 

 been adopted.* These valves are thin and 

 transparent, yet of considerable strength. Their 

 attached are thicker than their free margins. 

 That portion of the pulmonary artery which is 

 placed immediately above the attachment of the 

 semilunar valves bulges out and forms three 

 projections, named from their discoverer 

 sinuses of Valsalva. These sinuses are more 

 apparent in old than in young persons. 



Left auricle (auricula sinistra ; a. pos- 

 terior ; atrium sen sinus venarum pulmonalium, 

 a. aorticum). External surface. It occupies 

 the upper, posterior, and left part of the base of 

 the heart, arid receives the blood brought back 

 from the lungs by the pulmonary veins. The 

 only part of the left auricle that can be fairly 

 seen after the pericardium has been opened, 

 and none of the parts disturbed, is the appendix. 

 To see it properly the pulmonary artery and 

 aorta must be cut through and thrown forwards. 

 It is of a very irregular shape, some anatomists 

 comparing it to an oblong quadrilateral, others 

 to an irregular cuboidal figure. Posteriorly 

 it rests upon the spinal column, from which itis 

 separated by the parts mentioned in describing 

 the position of the heart itself, and appears as 

 if confined between the spine and base of the 

 heart, a fact which has been considerably 

 insisted upon in some of the explanations of the 

 tilting motion of the heart. Superiorly and to 

 the right it is connected to the auricle of the 

 opposite side. More anteriorly and still to the 

 right it is free, and is separated from the right 

 auricle by the aorta and pulmonary artery. Its 

 base is connected to the base of the corres- 

 ponding ventricle. The auricle is prolonged 

 forwards at first to the left, but bends towards 

 the right before terminating. This prolongation 

 is the appendix or proper auricle. This 

 appendix is longer, narrower, more curved, 

 more denticulated on the edges, and more 

 capacious than the corresponding part of the 

 right auricle, and projects along the left side of 

 the pulmonary artery, a little beyond and below 

 the anterior margin of the left ventricle. The 

 two left pulmonary veins enter the posterior 

 and left side, and the two right pulmonary 

 veins enter the posterior and right side of the 

 auricle. 



The left auricle, like the right, has been 

 divided into sinus venosus and proper auricle. 

 Inner surface. The inner surface may be 

 divided into, 1st, a posterior, which is smooth, 

 and which belongs exclusively to itself; 2d, an 



* I find that the late Dr. A. Duncan, jun. has 

 justly remarked that there is no necessity for calling 

 in the aid of the corpora Arantii to produce the 

 complete obstruction of the calibre of the artery, as 

 the free edges of these valves, when they are 

 thrown inwards* do not exactly lie in close apposition 

 but overlap each other* Besides these bodies are 

 occasionally very indistinct, and frequently do not 

 project beyond the free margin of the valves, 

 especially in the pulmonary semilunar valves* 



anterior, which communicates by a round 

 opening with the cavity of the appendix ; 3d, a 

 right, the anterior and greater part of which 

 is formed by the septum of the auricles. Upon 

 this is observed the fossa ovalis, but without 

 the distinct depression which it presented in 

 the right auricle. The upper margin of the 

 valve, between which and the upper thick edge 

 of the fossa ovalis the oblique aperture exists, 

 which we formerly stated to be frequently 

 observed here, is often distinctly seen in the 

 left auricle. The valvular nature of this small 

 slit must prevent any intermixture of the blood 

 of the two sides. This margin, when present, 

 looks forwards and to the left. The two right 

 pulmonary veins open upon this surface imme- 

 diately posterior to the septum, and between 

 the septum and posterior surface. 4th, A left, 

 into which the two pulmonary veins of the left 

 side open. 



The pulmonary veins of the two lungs are 

 thus separated from each other by the whole 

 breadth of the auricle. The veins of the same 

 side open into the auricle, the one immediately 

 below the other, so that they occupy the whole 

 height of the auricle. The superior is generally 

 the larger. The two veins of the same side 

 occasionally enter by a common opening, or 

 this may occur on one side only. At other 

 times we may have five openings. These veins, 

 like the cavee, have no valves at their termina- 

 tion in the auricle. At the lower and anterior 

 part of the auricle a large oval opening presents 

 itself. This is the left auriculo-ventricular 

 opening, and like that on the right side it has 

 its upper margin surrounded by a white tendi-* 

 nous ring. This ring, unlike that of the right 

 side, is everywhere sufficiently opaque to pre- 

 vent the fat placed in the auricular groove to 

 be seen through it. 



The inner surface of the left auricle differs 

 materially from that of the right in its greater 

 smoothness, and the consequently smaller num- 

 ber of its musculi pectinati. In fact, the only 

 place in which these are observed, and that too 

 to a comparatively smaller extent than in the 

 corresponding portion of the right, is the ap- 

 pendix. This arises from the greater strength 

 of the left auricle, the muscular fibres being so 

 closely laid together as not to leave any interval 

 between them. 



Left ventricle (ventriculus sinister, v.pos* 

 terior, v. aorticus.) External surface.- It is 

 of a conical shape, and occupies the posterior 

 and left part of the heart. It is rounded and 

 does not present the flattened appearance of 

 the right ventricle. It projects downwards 

 beyond the right, and forms the apex of the 

 heart. Though the left proceeds lower down 

 than the right ventricle, that portion of the right 

 called infundibulum or conus arteriosus mounts 

 higher than any part of the left. The left is on 

 the whole a little longer than the right. The 

 circumference of the base of the right ventricle 

 is greater than that of the left, exceeding it in 

 some cases in the injected heart by about two 

 inches. 



Internal surface. This ventricle is best 

 opened by making an incision close upon the 



