38 



ANATOMY. 



FIG. 16. 



THE THORAX. 



What is the Thorax? An osseo-cartilaginous cage formed by the bodit- 

 of the dorsal vertebrae posteriorly, the ribs and costal cartilages laterally, and 

 the sternum in front. Its shape is conical, the axis inclined forwards, the bast 

 below and closed by the diaphragm. 



What Structures pass through its Apex ? The trachea, oesophagus, 

 large vessels of the neck, pneumogastric, phrenic and sympathetic nerves, 

 thoracic duct, and in inspiration the apex of the lung. 



What Structures are contained in its Cavity ? The trachea, bronchi 

 and lungs, the heart and great vessels, internal mammary arteries, azygos and 

 bronchial veins, pneumogastric, phrenic, and splanchnic nerves, oesophagus, 

 thoracic duct, lymphatic vessels, and glands. 



THE STERNUM. 



Describe it. The sternum, or breast-bone, consists of 3 parts, the manu- 

 brium, or handle; the gladiolus/ or sword; and the ensi- 

 form or xiphoid appendix.^ It presents the 

 Interclavicttlar Notch, on its superior border. 

 Manubriump articulates with the clavicleX ist costal 



cartilage,* 1 and a part of the 2d.y r 



Gladiolus, articulates with the costal cartilages from the 

 3d to the 6th inclusive, and partly with the 2d and 7th. 

 Ensiform Appendix (the tip), articulates with the carti- 

 lage of the false ribs, and in part with the 7th costal 

 cartilage./ 



Describe its development and muscles. The ster- 

 num is developed by 6 centres, I each for the manubriumi 

 and ensiform aooendix, and 4 for the gladiolus. The mus- 

 cles attached to it are 9 pairs and one single muscle, 

 the sterno-cleido-mastoid, sterno-hyoid, and sterno-thyroid. 

 3, to its upper part ; the rectus abdominis, external and internal oblique, trans- 

 versalis, and the diaphragm, 5, to its lower part; the pectoralis major, I, an- 

 teriorly ; and the triangularis sterni, I, posteriorly. 



THE RIBS. 



Describe them. There are 12 ribs on each side, of which 7 are "true 

 ribs," being each connected to the sternum by a separate cartilage; and 5 are 

 " false ribs." Three of the latter are connected by their cartilages to the carti- 

 lage of the 7th rib, while two are called " floating ribs," having each one ex- 

 tremity free. 



What are the Characteristics Common to most of the Ribs ? They each 

 consist of a head, neck, and shaft, and present the following points, viz. 



