100 ANATOMY. 



Describe the Heart. It is a hollow muscular organ, conoidal in shape, 

 placed obliquely in the chest between the lungs, base upwards, apex towards 

 the left and front, corresponding to the interspace between the 5th and 6th 

 costal cartilages, one inch inside of and two inches below the left nipple. In 

 the adult its size is about 5 inches by 3^ by 2^, and from 8 to 12 oz. in 

 weight. 



What are the Cavities of the Heart ? They are 4 in number, an 

 auricle and a ventricle on each side of the heart, separated by a longitudinal 

 muscular septum, and indicated on the external surface of the organ by grooves, 

 named, from their contiguous cavities, as the Auricula-ventricular Groove trans- 

 versely, and the Inter- Ventricular Groove longitudinally. 



Describe the Right Auricle. It is larger than the left, can hold about 2 

 fluidounces, its walls being about I line in thickness. It receives the venous 

 blood by the superior and inferior venae cavaa and the coronary sinus, and 

 presents interiorly the following points for examination: 



Appendix Auricula, a conical pouch projecting from the auricle to the front 



and left, its margins being dentated. 

 Openings of the superior and inferior venae cavse and the coronary sinus, the 



latter having a valve in two segments. 

 Foramina Thebesii, several minute orifices, the mouths of veins from the 



substance of the heart. 

 Tubercle of Lower, a very small projection on the right wall, supposed to 



influence the direction of the blood-current. 

 Eustachian Valve, at the anterior margin of the inferior vena cava; large i/* 



the foetus, to direct the blood to the foramen ovale. 

 Fossa Ovalis, a depression on the inner wall, and the situation of the foramen 



ovale in the foetus. 



Annulus Ovalis, the oval margin of the fossa ovalis. 

 Musculi Pectinati, muscular columns on the inner surface of the appendix 



and the inner wall of the auricle. 



Auricula-ventricular Opening, communicates with the right ventricle, is oval, 

 about an inch broad, surrounded by a fibrous ring, and is guarded by the 

 tricuspid valve. 



Describe the Right Ventricle. Its form is conical, its cavity containing 

 about 2 fluidounces, its apex above the apex of the heart, and it presents in- 

 teriorly the following, viz. 



Tricuspid Valve, consists of 3 triangular segments connected by their base* 

 with the auriculo-ventricular orifice, and by their sides with each other, 

 the largest being on the left side. 



Chorda Tendince, delicate tendinous cords which connect the margins and 

 lower surfaces of the tricuspid valve with the columnse. 



