482 STRUCTURE OF THE HEART. 



between the auriculo-ventricular opening and the commencement of the 

 aorta, and acts the part of a valve to that foramen during the filling of the 

 ventricle. The difference in size of the two valves, both being triangular, 

 and the space between them, has given rise to the idea of a " bishop's 



Fig. 213.* 



mitre" after which they were named. These valves, like the tricuspid, 

 are furnished with an apparatus of tendinous cords, chorda tendinece, which 

 are attached to two very large columns carnece. 



The Columnce carnece admit of the same arrangement into three kinds, 

 as on the right side. Those which are free by one extremity, the columnar 

 papillares, are two in number, and larger than those on the opposite side ; 

 one being placed on the left wall of the ventricle, and the other at the 

 junction of the septum ventriculorum with the posterior wall. 



The Semilunar valves are placed around the commencement of the 

 aorta, like those of the pulmonary artery ; they are similar in structure, 

 and are attached to the scalloped border by which the aorta is connected 

 with the ventricle. The tubercle in the centre of each fold is larger than 

 those in the pulmonary valves, and it was these that Arantius particularly 

 described ; but the term " corpora Arantii" is now applied indiscrimi- 

 nately to both. The fossae between the semilunar valves and the cylinder 

 of the artery are larger than those of the pulmonary artery ; they are called 

 the "sinus aortici" (sinuses of Valsalva). 



STRUCTURE OF THE HEART. 



The arrangement of the fibres of the heart has been made the subject of 

 careful investigation by Mr. Searle, to whose article, "Fibres of the Heart," 



* The anatomy of the heart; the organ is viewed on its left side. 1. The cavity of 

 the left auricle. The number is placed on that portion of the septum auricularum cor- 

 responding with the centre of the fossa ovalis. 2. The cavity of the appendix auriculae, 

 near the apex of which are seen the musculi pectinati. 3. The opening of the two 

 right pulmonary veins. 4. The sinus, into which the left pulmonary veins open. 5. 

 The left pulmonary veins. 6. The auriculo-ventricular opening. 7. The coronary vein, 

 lying in the auriculo-ventricular groove. 8. The left ventricle. 9, 9. The cavity of the 

 left ventricle; the numbers rest on the septum ventriculorum. a. The mitral valve; 

 its flaps are connected by chordaa tendinese to 6, b. The columnae carneae. c, c. Fixed 

 co'u'nna? carnere, forming part of the internal surface of the ventricle, d. The arch of 

 th? aorta, irom the summit of which the three arterial trunks of the head and upper ex 

 trfjmities are seen arising, e. The pulmonary artery. /. The obliterated ductus arte- 



