

HEART. 115 



and the lower border of the third dorsal vertebra, where 

 the thoracic aorta begins. 



The bifurcation of the trachea is the division of that air- 

 tube into the right and left primary bronchi. These 

 divisions retain the structure of the trachea, and are made 

 up of similar though smaller and less perfect cartilaginous 

 rings. The right bronchus is about an inch in length, and 

 enters the lung above the right pulmonary artery. The left 

 bronchus is about two inches in length, and is smaller than 

 the right ; it passes obliquely downward under the arch of 

 the aorta, and enters the lung below the left pulmonary 

 artery. The bronchus, with the pulmonary artery and vein, 

 constitute what is called the root of the lung. 



The BRONCHIAL GLANDS, often numerous and of large 

 size, frequently surround the bifurcation of the trachea. 

 In the adult these are sometimes quite black from carbon- 

 aceous deposit, and in scrofulous subjects often contain 

 oftened tuberculous or cretaceous matter. 



HEART. 



The heart should now be removed for further examination by divid- 

 ing its vessels at such a point as not to mutilate the auricles. The 

 aorta must be cut across near the heart. 



The HEART is a muscular organ divided by septa into 

 two halves, right and left ; each half consisting of two 

 hollow portions, an auricle and ventricle, and each ventri- 

 cle, conical in shape, being surmounted by its own auricle ; 

 the two ventricles form the bulk of the viscus. The auri- 

 cles are quadrangular in shape, with a constricted part in 

 front called the appendix, and have much thinner walls 

 than the ventricles. The appendices auriculae project for- 

 ward with their indented margins, the left being the longest, 

 and nearly meet each other in front of the great vessels. 

 Externally each cavity is defined by a well-marked furrow 

 of separation, containing the ramifications of the vessels 

 destined to the proper nourishment of the heart; that 

 between the auricles and ventricles amounts almost to a 

 constriction of the organ. A quantity of fat fills up the 

 sulcus that would otherwise be formed. 



The anterior surface of the heart may be distinguished 

 from the posterior by the appendices of the auricle, which 

 meet in front and not behind, and by the pulmonary artery 

 which lies in front of the aorta. The left ventricle is the 

 thickest and forms the apex of the viscus, a fact which is 



