Bones of the Thorax. 



81 



101 and 102. Eleventh and twelfth ribs of right 

 side, costae XI et XII, from below. 



The costa XI is like the costa XII (see also figures 106 and 107), a 



delicate bone in which there can be sharply made out only a small capitulum behind 

 without crista capituli; the collum costae and tuberculum costae are practically absent 

 as are also the angulus costae and the sulcus costae. The two ribs are, in their 

 whole length, directed nearly evenly obliquely downward and curved so as to be almost 

 evenly convex lateralward and backward. The cross section shows rounded angles; in 

 front the ribs become sharper and possess generally only a small cartilaginous tip. 

 They form no joint union with the other ribs; but end free between the abdominal muscles. 



The twelfth rib is very variable in its length; when it is long, it runs parallel 

 to the eleventh rib ; when it is short, it runs more transversally and resembles the proc. 

 transversus of a lumbar vertebra. 



Between every two adjacent ribs is an intercostal space, spatium inter- 

 COStale (see Figs. 105 107). Its form resembles that of the adjacent ribs and 

 varies with their shape and position. 



Spalteholz, Atlas. 



