476 RIBS AND STERNUM. BONES OF SHOULDER. 



connected with the cartilage of the seventh rib ; while the 

 other two ribs, being completely unattached at the anterior 

 ends, are termed floating ribs. The sternum or breast-bone 

 is flat and of simple form in Man ; but it is much larger in 

 many other animals. In those which have need of great 

 strength in the upper limbs, such as Birds, Bats, and Moles, 

 it is not only increased in breadth, but is furnished with a 

 projecting keel or ridge for the attachment of powerful muscles 

 (fig. 250). In the Turtle tribe, on the contrary, it is very 

 much extended on the sides, so as to afford, with the ribs, a 

 complete protection to the contained parts ( 83). 



634. We have next to consider the structure of the members 

 or appendages which are attached to this central framework. 

 These are spoken-of as superior and inferior, when we are 

 treating of Man, whose erect posture places one pair above 

 the other : but when the ordinary Quadrupeds are alluded to, 

 they are termed anterior and posterior, one pair being in front 

 of the other. Each member consists of a set of movable 

 bones, which serve as levers ; but the socket in which the 

 first of these works, is formed by a bony framework, which is 

 connected more or less closely with the spinal column. This 

 framework, in the upper extremity, consists of the Scapula 

 or blade-bone, and the Clavicle or collar-bone. In the lower 

 extremity, it is formed by a set of bones, the union of which 

 with the sacrum completes the Pelvis or bason at the bottom 

 of the spinal column (fig. 223). 



635. The Scapula is a large flat bone, which occupies the 

 upper and external 1 part of the back. Its form is somewhat 

 triangular ; and at its upper and outer angle is a broad but 

 shallow cavity, destined to receive the head of the humerus 

 or arm-bone. Above this cavity is a large projection, termed 

 the acromion-process, which is united by ligaments, &c , with 

 the external end of the clavicle, and thus forms the bony 

 eminence that we feel at the top of the shoulder. A little 

 internally to this we find another process, the coracoid, which 

 only serves in Man for the attachment of certain muscles, but 

 which in Birds is developed into a distinct bone ( 668). 

 The hinder surface of the scapula is divided into two by a 

 projecting ridge or keel, which gives a more extensive and 



1 The term external is continually used in Anatomy, to describe the 

 parts furthest removed from the central or median line of the body. 



