THE HEART. 



599 



the auricles, the effect of which is the repletion of the ventricles. 3. The systole 

 of the ventricles, propelling the blood into the arterial systems ; after which 

 comes another period of general diastole. 



Differential Characteks in the Heart of the other Animals. 



In the Ox, Sheep, and Goat, the ventricular mass of the heart is more regularly conical 

 than in Solipeds; it has three longitudinal grooves, one of which is accessory and passes 

 behind the (left) ventricle. 



In the Ox two small bones, named cardiac bones, are found in the substance of the aortic 

 zone. The largest is in the right side, at the point where the arterial ring is approximated to 

 the auriculo- ventricular zones; the other, situated in the left, is perhaps not constantly 

 present. The first is triangular in shape, curved to the right, and its base is directed 

 upwards. The right face lies against the auriculo-ventricular opening; the left is covered by 

 the walls of the aorta at its commencement. It is about an inch in length. (The Ox's heart 

 averages from about 3^ to 4^ lbs. ; that of the Sheep, from 5J to 7 oz. It is more elongated and 

 pointed in Ruminants than in the Horse or Pig. The large bone in the Ox's heart is elongated 

 from before to behind, flattened laterally and curved to the left; its surface is roughened, and 

 its lengtii is sometimes about 2 inches. 



The left, or small bone, is usually flat- 

 tened on each side and triangular, one 

 of its points is directed forwards, another 

 backward, and a third inferioriy; its 

 length is about three-quarters of an 

 inch when fully developed. Besides the 

 Ox, a small cross-shapeil bone is found 

 in the heart of the Sheep, Pig, Camel, 

 Deer, Giraffe, and sometimes in the 

 Horse. Remak found in the pericar- 

 dium of the Ox, at the border of the 

 left auricle, a row of villi similar to those 

 discovered in the border of the chicken's 

 heart.) 



The heart of the Pig resembles that 

 of the Horse; its direction is a little 

 more oblique, and 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 

 ovoid or nearly globular. It rests al- 

 most entirely on the upper face of the 

 sternum ; its anterior face has become 

 the inferior, and its point, directed 

 backwards, touches the anterior surface 

 of the diaphragm. The pericardium is 

 attached to the aponeurotic centre of the 

 diaphragm. 



Comparison of the Heart of Man 

 with that of Animals. 



Fig 35<^ 



HUMAN LUNGS AND HEART (FRONT VIEW). 



1, Right ventricle; 2, left ventricle; 3, right auricle; 

 4, left auricle ; 5, pulmonary artery ; 6, right 

 pulmonary artery ; 7, left pulmonary arteiy ; 8, 

 ligament of ductus arteriosus; 9, arch of aorta; 

 10, superior vena cava; 11, 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 ; 2.S, inferior lobe , 24, superior lobe 

 of left lung ; 25, inferior lobe. 



Tho human heart is ovoid, and 

 similar to that of Carnivora ; the ventri- 

 cular mass is not acute at its apex, as in Solipeds and Ruminants. Its direction is modified 

 in consequence of the antero-posterior flattening of tlie 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 border is in him the right border, and the posterior the 

 left border. 



The organ is suspended obliquely downwards, forwards, and to the left ; consequently, the 

 right auricle is to the right of the sternum, between the third and fourth ribs, and the point 



