Dissection of Sheeph Heart. 157 



Dissection of Right Aurict.e. In order to examine tlie 

 interior of the right Auricle it will only be necessary to make 

 one incision, viz. from the point of entrance of the Yena Cava 

 inferior to the Auricular appendage ; and to remove and wash 

 out the blood. 



Around and in the interior of the Appendix are fleshy bands, 

 named Musculi Pectinati, which form a net-work contrasting 

 with the general smoothness 6f the Auricle. Immediately 

 opposite the termination of the Inferior Cava is a large oval 

 depression. Fovea, seu Fossa Ovalis, which is the vestige of the 

 Foramen Ovale of the Footal Heart, and indicates the original 

 place of communication between the two Auricles ; it is bounded 

 by a prominent ridge of muscular fibre called Annuhis, seu Isth- 

 mus Vieussenii : a thin semitransparent structure closes the 

 Fossa and forms the Septum Auricularum. In front of and be- 

 neath the Inferior Cava is a thin fold of the lining membrane of 

 the cavity, a rudiment of the Eustachian Valve, a remnant of a 

 much larger structure in the Foetus by which the blood from the 

 Inferior Cava was directed through the Foramen Ovale into 

 the left Auricle. Immediately beneath the Eustachian Yalve 

 is the dilated orifice of the left Yena Azygos ; at its termination 

 and almost within the Auricle may be seen the mouths of the 

 smaller veins of the Heart (venae cordis minimse; named the 

 Foramina Thehesii. Between the openings of the Superior and 

 Inferior Cava, on the right side of the wall of the Auricle is 

 a small projection termed the Tubercle of Lower : it was sup- 

 posed by Lower to direct the blood from the Superior Cava 

 towards the Auriculo-ventricular opening {i.e. the opening 

 between the Auricle and Yentricle) . The orifice of the Superior 

 Cava is not provided with a valve. 



In the Adult there is but one current of blood in the right 

 Auricle, viz. towards the Yentricle : but in the Foetus thero 

 are two streams in the cavity of the Auricle : one of pure and 

 the other of impure blood, which cross one another in early 



