OF THE CHEST 35 



breastbone by the interposition of cartilages, or 

 gristle, of a substance softer than bone, and more 

 elastic and yielding. By this quality they are 

 fitted for protecting the chest against the effects 

 of violence, and even for sustaining life after the 

 muscular power of respiration has become too 

 feeble to continue without this support. 



If the ribs were complete circles, formed of 

 bone, and extending from the spine to the breast- 

 bone, life would be endangered by any accidental 

 fracture ; and even the rubs and jolts to which 

 the human frame is continually exposed would be 

 too much for their delicate and brittle texture. 

 But these evils are avoided by the interposition 

 of the elastic cartilage. On their forepart the 

 ribs are eked out, and joined to the breastbone by 

 means of cartilages, of a form corresponding to 

 that of the ribs, being, as it were, a completion of 

 the arch of the rib, by a substance more adapted 

 to yield in every shock or motion of the body. 

 The elasticity of this portion subdues those shocks 

 which would occasion the breaking of the ribs. 

 We lean forward, or to one side, and the ribs 

 accommodate themselves, not by a change of 

 form in the bones, but by the bending or elasticity 

 of the cartilages. A severe blow upon the ribs 

 does not break them, because their extremities 

 recoil and yield to the violence. It is only in 

 youth, however, when the human frame is in per- 



