122 LECTURE III. 



rant upon its basis, in the manner I have 

 formerly mentioned* 



The upper or pectoral extremity of man, 

 is divided into the shoulder, which is 

 composed of two bones > the arm of one ; 

 the fore-arm of two j and the hand of many. 

 The blade-bone of the shoulder is placed 

 behind the chest, and not, as in brutes, by 

 the side. It is in common so situated that 

 the cup to which the arm is joined, and 

 from which it hangs, projects exactly in the 

 lateral direction, and consequently the 

 weight of the arm has no tendency to move 

 its socket forwards or backwards, but 

 merely to depress it. Though the bones 

 of the shoulder can be moved forwards and 

 backwards, upwards and downvi'ards, even 

 in a considerable degree ; yet the joint 

 of the shoulder can never approach to the 

 breast bone as it does in quadrupeds. The 

 effects resulting from these circumstances 

 are, that when the arms hang in their 

 natural direction, the general line of gra- 

 vity of the upper part of the body un- 



