THE RIBS. 



FIG. 17 



Head,* is divided by a ridge into 2 facets, which articulate with the facets on 

 the bodies of the dorsal vertebrae ; the ridge giving attachment to the in- 

 terarticular ligament. 



Neck, about an inch long, having attached to its upper border the anterior 

 costo-transverse ligament, to its posterior surface the middle costo-trans- 

 verse ligament ; its anterior surface is smooth. 

 Tuber osity,t> 

 at the junc- 

 tion of the 

 neck with 

 the shaft, 

 has a facet 

 for articula- 

 t io n with 

 the trans- 

 verse pro- 

 cess of the 

 next lower 

 vertebra, and a rough surface for the posterior costo-transverse ligament 



Shaft, twisted on itself, is concave internally, convex externally, its uppef 

 border round and smooth, its lower border grooved^ for the intercostal 

 *vessels and nerves. At its external extremity* is an oval depression for 

 the insertion of the costal cartilage. 



Angle,* just in front of the tuberosity, is marked by a rough line, to which 

 are attached the muscles of the deep layer of the back. 



How are they developed ? Each rib has 3 centres, one each for the 

 head, shaft, and tuberosity. The last 2 ribs, having no tuberosity, are devel- 

 oped each by 2 centres. 



Describe the Peculiar Ribs. They are the ist, 2d, loth, nth, and I2th. 

 They respectively present the following peculiarities, viz. 



ist Rib, is broad, short, not 

 twisted, has no angle, only one 

 facet on the head ; but on its 

 upper surface are seen tivo 

 grooves for the subclavian ar- 

 tery^ and vein,* and between 

 them a tubercles for the scale- 

 nus anticus muscle. 



2d Rib, is not twisted, its tuber- 

 osity and angle are very close 

 together, and its upper surface presents rough surfaces for the serratus 

 magnus and scalenus posticus muscles. 



FIG. 18. 



