INTERCOSTAL MUSCLES. 



241 



tubercles of the rib, nearly to the outer end of the cartilages ; but 

 in the two lowest ' intervals they reach forwards to the ends of the spaces. 

 Thin tendinous fibres, having the same direction as the external intercostal 

 muscles, are continued forwards between the costal cartilages from the points 

 where the muscles cease to the sternum, and there cover the internal 

 intercostals. 



Fig. 193. 



Fig. 193. VlEW OF SEVERAL OF THE MlRDLE DORSAL VERTEBRA AND RlBS, TO SHOW 



THE INTERCOSTAL MUSCLES (after Cloquet). ^ 



A, from the side ; B, from behind. 



IV, the fourth dorsal vertebra ; V, V, the fifth rib and its cartilage ; 1, 1, the levatorea 

 costarum muscles, short and long ; 2, the external intercostal muscles in the upper of the 

 two intercostal spaces represented ; 3, the internal intercostal layer shown in the lower 

 of the two spaces represented by the removal of the external layer, and seen in A in the 

 upper space, where the external layer terminates in front : the deficiency of the internal 

 layer towards the vertebral column is shown in B. 



The internal intercostal muscles, placed deeper than the preceding, 

 are attached to the inner margins of the ribs and their cartilages. Com- 

 mencing at the anterior extremities of the cartilages of the ribs, they extend 

 as far back as a point within the angles of those bones. The fibres incline 

 downwards and backwards, crossing those of the external intercostals ; 

 they are, however, somewhat shorter and less oblique in their direction. 



The internal are separated from the external intercostal muscles at the back of the 

 spaces by the intercostal vessels and nerves ; they are lined internally by the pleura. 



The levatores costarum y twelve on each side, arise from the tips of the 

 transverse processes of the seventh cervical and eleven highest dorsal ver- 

 tebrae. Corresponding in direction with the external intercostal muscles, on 

 which they lie, they pass downwards and outwards, spreading as they 



