176 APPLIED ANATOMY. 



Emphysema of the surface of the body may ensue, but is not dangerous. Pneumo- 

 thorax, which may be accompanied by infiltration of air into the lung tissue, is more 

 dangerous, favoring collapse of the lung. The object of treatment is to keep the 

 chest-walls from moving. This is accomplished by strapping the chest with adhesive 

 plaster, which is usually laid on almost in the direction of the ribs ; but as the chest 

 moves with respiration, the ribs rising, and as they slope downward and forward, I 

 have preferred to lay the straps on from in front downward and backward, this tends 

 to prevent the ribs from rising in inspiration. 



THE THORACIC VERTEBRA. 



The thoracic or dorsal vertebrae are twelve in number and are so articulated 

 with one another as to form a single, regular curve with its concavity forwards and 

 convexity backward. Any sudden change in the direction of the curve is an evidence 

 of disease; this is seen in the angular curvature of Pott's disease or caries of the 

 spine. The ribs are connected with the vertebrae by the articulation of the head of 

 the rib with the body of the vertebra, and the tubercle of the 'rib with the transverse 

 process. The transverse process is connected with the body by the pedicle and with 

 the spinous process by the lamina. The spinal cord is exposed in operations by 

 removal of the spinous process and laminae, hence the name laminectomy. 



The spinous processes are the guides which indicate the position and condition 

 of the vertebrae. Their tips are not covered by muscles but lie close beneath the 

 skin and are readily felt and any abnormality detected. In the normal body the 

 grooves on each side of the spinous processes are filled up with muscle, but in certain 

 diseases, as in infantile paralysis and lateral curvature, they become atrophied and 

 the spine becomes twisted, hence on the convex side of the abnormal lateral curve, 

 to the outer side of the spines, the projection formed by the transverse processes and 

 tubercles of the ribs can be both seen and felt. 



The external curve formed by the tips of the spinous processes of the thoracic 

 region in the normal person is not so great as is the curve formed by the anterior 

 portion of the bodies of the thoracic vertebrae. This is because the spinous 

 processes at the upper and lower portions of the chest project out almost at right 

 angles to the long axis of the body, while those of the middle portion slope down- 

 ward. Hence the tips of the spinous processes of the seventh cervical, first dorsal, 

 and twelfth dorsal vertebrae are opposite the bodies of the same vertebrae, while the 

 others are opposite the bodies of the vertebrae next below. (The spine will be 

 considered more at length in the section devoted to the Back. ) 



SOFT PARTS. 



The bony thorax is lined by the pleurae, the ribs are united to each other by 

 the intercostal muscles, and over all are muscles, superficial fascia, and skin. In 

 addition, in front are the mammary glands and behind are the scapulae. 



THE INTERCOSTAL MUSCLES AND ARTERIES. 



The intercostal spaces are occupied by the two intercostal muscles, with a fascia 

 above them, one below, and one between them. 



The external intercostal muscles run downward and forward. They begin at 

 the tubercles of the ribs posteriorly and end at the costal cartilages anteriorly. 

 They are continued forward to the sternum by the anterior intercostal membrane, 

 formed by the fusing of the outer and middle intercostal fascias. The internal 

 intercostal muscles go downward and backward. They begin at the sternum and 

 end at the angles of the ribs. They are continued to the spine by the posterior 

 intercostal membrane, formed by the fusing of the middle and internal intercostal 

 fascias. The intercostal arteries come from both anteriorly and posteriorly. The 

 anterior intercostals come from the internal mammary for the upper five or six 

 spaces and from the musculophrenic artery for the remainder. They arise either 

 as a single trunk or as separate superior and inferior branches. At first they are 

 between the pleura and internal intercostal muscle, but they soon perforate that 



