594 



HEART. 



Fig. 276. 



large veins. These fibres cross transversely 

 between the anterior surface of the two auricles 

 and connect them together. These superficial 

 fibres are also prolonged into the interauricular 

 septum (fig. 277, f) to assist in forming the 



Fig. 277. 



circular band of fibres which surrounds the 

 fossa ovalis. Gerdy figures a superficial band 

 of fibres (Jig- 276, 6) as belonging exclusively 

 to the left auricle. 



The deep fibres belong exclusively to a sin- 

 gle auricle. They are superficial at various 

 parts, where the external or circular fibres are 

 deficient. By their inner surface they are con- 

 nected to the inner membrane of the auricles, and 

 a thin layer of cellular tissue unites their outer 

 surface to the inner surface of the superficial 

 fibres. In the left auricle Gerdy describes, 

 1st, a left auricular loop (fig. 276, c c, fig. 277, 

 c c), which embraces the auricle from its su- 

 perior edge to its base, which runs a little 

 obliquely to the left, before, above, and then 

 behind the auricle, and is attached by its ex- 

 tremities to the auricular tendinous ring near 

 the septum. It is contracted at that part where 

 it passes between the pulmonary veins. 2d. 

 The pulmonary veins are surrounded by circu- 

 lar fibres (fig. 276, d d, fig. 277, d d), which 

 are continued along their course to a variable 

 extent,' sometimes they merely surround the 

 termination of one or more of these veins, 

 at other times I have seen them prolonged out- 

 wards as far as the roots of the lungs. These 

 fibres generally form a continuous layer, and 



of sufficient thickness to render them capable 

 of constricting these vessels considerably. 3d. 

 Some fibres proper to the appendix (fig- 276, 

 m m\ which, by passing between and uniting 

 themselves to the other fibres of the appendix, 

 form that reticulated appearance which it pre- 

 sents in its inner surface. Some of these fibres 

 are circular, others form incomplete circles. 



In the right auricle, Gerdy has described, 

 1st, a right auricular loop (Jig. 276, h A, fig. 

 277, A), which is attached anteriorly to the 

 tendinous structure at tne base of the auricle ; 

 it extends upwards in the anterior edge of the 

 septum auriculorum ; it then curves round the 

 fossa ovalis, of which it forms the projecting 

 edge, and at the orifice of the vena cava supe- 

 rior it divides into a right and left band. The 

 first proceeds downwards, becomes engaged 

 with some of the superficial fibres around the 

 cava superior, and forms the angle between 

 them (tuberculum Loweri), from which it 

 passes downward to the auricular tendinous 

 ring along the right side of the cava inferior. 

 The left division passes along the left side of 

 the cava inferior, in the posterior edge of the 

 auricular septum, where it intermixes with the 

 fibres which embrace the entrance of the coro- 

 nary vein. 2d, Some muscular fibres (fig. 

 276, p\ which pass between the anterior part 

 of the tendinous ring and the appendix. 3d, 

 Some circular fibres, which surround the en- 

 trance of the cava superior (fig. 276, o) : these 

 do not extend upwards beyond the orifice of 

 the vein. 4th, The bundles of fibres which 

 arise from the right side of the auricular ring 

 proceed upwards to the posterior part of the 

 appendix, and form the musculi pectinati 

 seen in the interior of the auricle. 5th, A few 

 fibres proper to the auricle (fig. 276, n\ which 

 assume the circular form. The action of all 

 these fibres superficial as well as deep must be 

 to diminish the capacity of their cavities, and 

 draw them towards the auriculo-ventricular 

 openings, and thus favour the passage of their 

 contents through these openings. 



Inner membrane of the heart. Each side of 

 the heart has its own lining membrane, and 

 both of these are closely allied to the serous 

 membranes in structure and appearance. They 

 are continuous with the inner coat of the vessels 

 which open into their different cavities. These 

 have been termed the endocarde by Bouillaud 

 to distinguish them from the serous coat of the 

 pericardium on the outer surface of the heart. 

 If we commence to trace the inner membrane 

 of the right side from the entrance of the two 

 cavae, we find that it is folded upon itself to 

 form the Eustachian valve at the entrance of 

 the inferior cava ; it then passes upon the inner 

 surface of the auricle, and at the opening of the 

 coronary vein it is again folded upon itself to 

 form the valve of the coronary vein. It passes 

 through the auriculo-ventricular opening, ad- 

 heres to the inner surface of the tendinous ring, 

 and is there folded upon itself to assist in form- 

 ing the tricuspid valve. It now proceeds upon 

 the inner surface of the ventricle, and at the 

 origin of the pulmonary artery it assists in 

 forming the semilunar valves, and becomes con- 



