514 



THE CIRCULATOBT APPASATUS. 



a,nd the pericardium is fixed to the sternum from the third rib to the xiphoid appendix, 

 as well as to the diaphragm. (The cartilage is not ossified until a late period.) 



In the Dog and Cat, the heart is oval or nearly globular. It is almost entirely resting 

 on the ujiper face of the sternum ; its anterior face has become the inferior; and its 

 point, directed backwards, touches the anterior surface of the diaphragm. The pericai-dium 

 is attached to the aponeurotic centre of the diaphragm. 



COMPAKISON OF THE HEATIT OP MAN ■WITH THAT OP ANIMALS. 



The human heart is ovoid, and similar to that of the Camivora ; the ventricular mass is 



not scute at its apex, as in 

 Fig. 265. Solipeds and Ruminants. Its 



direction is modified in conse- 

 quence of the antero-posterior 

 ilatteiiing of the chest. It is 

 situated across the median plane 

 of the thorax , its right face in 

 animals has become the anterior 

 face in Man, and is applied to the 

 sternum; the anterior bnrder ia 

 in him the right border, and the 

 posteiior the left border. 



The organ is suspended ob- 

 liquely downwards, forwards, and 

 ti I thii left ; consequently, the right 

 auricle is to the right of the 

 sternum, between the third and 

 fourth ribs, and the point on a 

 level with the sixth left inter- 

 costal space. The auricular ap- 

 pendages, paiticularly the right, 

 are more rounded and bulging 

 than in animals. The pulmonaiy 

 veins, four in number, open on 

 the upper face of the left auricle. 

 There are no essential dilfcr- 

 ences to be noted in its internal 

 conformation. We may indicate 

 the pi-esence of a fold that passe.i 



HUMAN LUNGS AND HEART; FKONT VIEW. 



1, Eight ventricle 2, Left ventricle ; 3, Right auricle ; 

 4, Left auricle ; 5, Pulmonary artery ; 6, Right 



pulmonary artery; 7, Left pulmonary artery ;° 8, fronf 7re7rng rfVieussens toThe 



opmmg ot the interiorvena cava: 

 this is the JHustachiun valve. We 

 may also mention the 'I'hebesian 

 valve at the entrance of the coro- 

 nary vtin. 



The fibrous rings and muscular 

 fasciculi are disposed as in the 

 Horse. 



The pericardium is a conical 

 sac ; but instead of its base being 

 ., ,. ,„.,,., presented upwards, it rests against 



the aponeurotic centre of the diaphragm: its summit is lost among the largo vessels, 

 and it adheres to the posterior face of the sternum. 



Ligament of ductus arteriosus ; 9, Arch of aorta ; 

 10, Superior vena cava; H, Arteria innominata; 12, 

 Right subclavian vein, with the artery behind it ; 

 13, Right common carotid artery and vein , 14, Left 

 vena innominata, 15, Left carotid artery and vein; 

 16, Left subclavian vein and artery; 17, Trachea; 

 18, Right bronchus ; 19, Left bronchus ; 20, 20, 

 Pulmonary veins; 21, Superior lobe of right lung; 

 22, Middle lobe ; 23, Inferior lobe ; 24, Superior lobe 

 of left lung ; 25, Inferior lobe. 



