100 PRACTICAL ANATOMY. 



acter, is thin, often curved, and terminates in a blunt 

 point, which is sometimes bifid. Occasionally a foramen 

 perforates the appendix. At each superior angle is a 

 half-facet for articulation with the costal cartilage of the 

 seventh rib. The ensiform appendix affords attachment 

 below to the linea alba, posteriorly to some fibres of 

 the diaphragm. 



The sternum is developed by six centres : one for the 

 manubrium, four for the gladiolus, and one for the 

 upper part of the ensiform appendix. 



THE COSTAL CARTILAGES 



are arranged in ten pairs, of which the upper five are 

 true costal cartilages and the lower five false. The true 

 costal cartilages are those which pass directly from the 

 sternal extremity of the rib to the sternum ; the false 

 costal cartilages are those which are more or less con- 

 nected together. They are highly elastic, cartilaginous 

 structures, which seldom undergo ossific change. The 

 cartilages are flattened, the upper ones rather less, being 

 oval on section. They increase in length from the first 

 to the seventh ; the upper four are directed nearly hori- 

 zontally inward, the fifth and those below pass upward 

 and inward ; the sixth and seventh are connected by a 

 single broad piece of cartilage ; the eighth is attached 

 to the seventh, and is also inserted into its inferior border 

 about an inch external to the sternum ; the ninth and 

 tenth are similarly arranged. The anterior extremities 

 of the eleventh and twelfth ribs articulate with short, 

 spur-like pieces of cartilage, the apices of which are free. 



THE RIBS. 



The ribs consist of twelve pairs of flat bones, which 

 assist in forming the posterior, lateral, and anterior wall 

 of the chest. They are divided into five true, five false, 



