NOTE ON THE CONHGUEATION OF THE HEAET. 73 



mo/a is indicated on the surface of the chest-wall by a line 

 drawn from the sternal end of the upper surface of the third 

 rif/ht costal cartilage to the seventh costo-stemal articulation. 

 This line is sHghtly curved, with its concavity looking inwards, 

 the summit of the curve being 1| inches from the middle 

 line. It corresponds to the right border of the right auricle in 

 its entire vertical extent (Plate IV. figs. A. + B., R.B.). 



This border terminates by meeting the right extremity of the 

 margo acutus at almost a right angle (Plate IV. fig. A.). 



The remaining borders which may be made out in the heart, 

 specially hardened in formalin, are the ma/ryo oUusus or left 

 ventricular border, and a border separating the back of the 

 auricles from the facies drnphroz/matuxi. From its position it 

 may be called a posterior border (Plate IV. fig. B., P.B.). As we 

 descend in the animal scale it becomes less marked. I found it 

 distinct in the hearts of two gibbons which I examined. 



Belatiom of the horders of the hcfxrt to the anterior chest^mll. 

 — These are given in most text-books, so I shall merely point 

 them out. The right or auricular border has already been 

 indicated. It takes a vertical but slightly curved course. The 

 margo acutus runs transversely or nearly so from the seventh 

 right chondro-sternal articulation to the apex. The latter is 

 situated on the fifth left intercostal space, 3^ inches from 

 the middle line. The margo obtusus (left border) extends 

 from the apex upwards and inwards to the lower surface of 

 the second left chondro-sternal articulation. To complete the 

 configuration of the heart we must indicate on the surface the 

 upper limit. This " is represented by a line passing from the 

 lower border of the second costal cartilage of the left side to 

 the upper border of the third cartilage of the right side." 

 {QiwAn.) 



I mention these surface markings of the borders of the heart 

 because I wish to point out that the figure thus mapped out on 

 the anterior chest-wall correspomds in outline to the configuration 

 of the formalin heart as seen from the front. But to demonstrate 

 this, it is not even necessary to harden the viscus. Open the 

 pericardium from the front carefully by a crucial incision, and 

 having separated the flaps, view the heart in situ. Its configura- 

 tion will be seen to correspond to that of the anterior aspect of 



