CHAPTER VIII. 



THE RIBS. 



The ribs form a series of long, narrow, and more or less 

 flattened bones, extending laterally from the sides of the 

 vertebral column, curving downwards towards the median 

 line of the body below, and mostly joining the sides of the 

 sternum. 



Free ribs are normally only attached to the thoracic ver- 

 tebras, although, as before shown, certain parts, which may 

 be serially homologous with ribs, are found in other regions 

 of the vertebral column ; but in such cases they become 

 ankylosed with their corresponding vertebrae. In the 

 thoracic region, the ribs are never normally ankylosed 

 with the vertebrae, but are articulated to them by synovial 

 joints, which permit a certain, though limited, amount of 

 motion. 



As a general rule, the first thoracic rib joins the pre- 

 sternum or manubrium ; sometimes, as in the Whalebone 

 Whales, this is the only rib united below to the sternum, but 

 usually a larger number are so connected, while the more 

 posterior are either attached by their extremities to the 

 edges of the ribs in front of them, and thus indirectly join 

 the sternum, or else they are quite free below, meeting no 

 part of the skeleton. These differences have given rise to 



