THE RIBS 



131 



epiphyses fuse with the ribs about the twenty-third year. 

 mainly at its line of junction with the costal cartilage. 



The rib-shaft increases in length 



Variations in the Number and Shape of the Ribs 



The ribs may be increased in number by addition either at the cervical or lumbar end of the 

 series, but it is extremely rare to find an additional rib or pair of ribs in both the cervical and 

 lumbar regions in the same subject. 



Fig. 157. — Rib at Puberty. 



Epiphysis for the head. Appears at 

 fifteen; fuses at twenty-three 



Epiphysis for tubercle. Appears at 

 fifteen; fuses at twenty-three 



The cartilaginous shaft commences to 

 ossify at the eighth week of intra- 

 uterine life 



Fig. 158. — The Thorax at the Eighth Fcetal Month. 

 (On the left side eight cartilages reach the sternum.) 



Cervical ribs are fairly common; as a rule, they are of small size and rarely extend more than 

 a few millimeters bevond the extremity of the transverse process (see p. 35). Rarely 

 they exceed such insignificant proportions' and reach as far as the sternum; betweeri these two 

 extremes many varieties occur. In one case Turner was able to make a thorough dissection of 

 a specimen in which a complete cervical rib existed. Its head articulated with the body of the 



