PECULIAR RIBS. 



131 



Structure. The ribs consist of cancellous tissue enclosed in a thin, compact layer. 



Development. Each rib, with the exception of the last two, is developed by 

 three centres : one for the shaft, one for the head, and one for the tubercle. The 

 last two have only two centres, that for the tubercle being wanting. Ossification 

 commences in the shaft of the ribs at a very early period, before its appearance in 

 the vertebi'ae. The epiphysis of the head, which is of slightly angular shape, and 

 that for the tubercle, of a lenticular form, make their appearance between the six- 



Angle 



slightly marked 



and close, to 



tuber osity. 



First serration 

 / Serratus magnus. 



KT> 8C 



Flu. 89. 

 Hinyle articular facet. 



FIG. 90. 

 Single articular facet. 



FIG. 91. 



Kinglc articular facet. 



FIGS. 87-91. Peculiar ribs. 



teenth and twentieth years, and are not united to the rest of the bone until about 

 the twenty-fifth year. 



Attachment of Muscles. To nineteen : The Internal and External intercostals, 

 Scalcnus anticus, Scalenus medius, Scalenus posticus. Pectoralis minor, Serratus 

 magnus, Obliquus cxternus, Quadratus lumborum, Diaphragm, Latissimus dorsi, 

 Serratus posticus superior, Serratus posticus inferior, Ilio-cOstalis, Musculus acces- 

 sorius ad ilio-costalem, Longissimus dorsi, Cervicalis ascendens, Levatores costarum, 

 and Infracostales. 



