Tin-: RIBS 



101 



for the scalenus anticus muscle. The groove in front of this surface is for the sub- 

 clavian vein, the groove behind it is for the subclavian artery. Between the groove 

 for the artery and the angle there is a rough surface for the scalenus medius muscle; 

 anterior to this rough surface and close beside the groove is an area from which the 

 first digitation of the serratus magnus takes origin. The under surface is smooth 

 and lacks a groove. The outer border is thick, and rounded for the internal and 

 external intercostal muscles. 



The costal cartilage of this rib fuses Avith the manubrium of the sternum; occa- 

 sionally the sternal extremity and costal cartilage of this rib are rei»laced by fibrous 

 tissue. " When a well-developed cervical rib is present, the head of the first may 

 present two facets as in a typical rib. 



The first rib, with its costal cartilage, gives attachment to the following 

 muscles : — 



Internal intercostal. 

 External intercostal. 

 Levator costee. 

 Scalenus anticus. 

 Scalenus medius. 



Sul»clavius (costal cartilage). 

 Sterno-hyoid (costal cartilage). 

 Pectoralis major (costal cartilage). 

 Serratus magnus. 

 Musculus accessorius. 



Fig. 110. — The Vertebral Ends of Texth. Elevexth, axd Twelfth Ribs. 



ANGLE 



SINGLE FACET (SOMETIMES 

 TWO FACETS ARE PRE- 

 SENT) 



SINGLE FACET (THIS RIB 



HAS AN ANGLE. BUT NO 



TUBEROSITY AND NO 

 NECXi 



SINGLE FACET (THIS RiB 

 HAS NEITHER TUBER- 

 OSITY, ANGLE, NOR NECKl 



xn 



Blood-supply, — This is derived mainly from the superior intercostal branch of 

 the subclavian artery. 



The second rib,' like the first, is strongly curved; its posterior angle is faintly 

 marked; and the shaft, like that of the first, can lie flat on the table. It has a 

 prominent anterior angle for the serratus magnus. 



It gives attachment to the following muscles : — 



Internal intercostals (first and second). Serratus magnus. 



External intercostals (first and second). Serratus posticus superior. 



Levator costse. Scalenus posticus. 



Pectoralis major (costal cartilage). Musculus accessorius. 



Cer\acalis ascendens. 



Blood-supply. — ^Superior intercostal branch of the subclavian artery, and the 

 first aortic intercostal. 



