LECTURE III. 127 



in their pectoral extremities; for the arm 

 and shoulder blade lie hid in the bulk and 

 circumference of the body. The back part 

 of the elbow in man, is formed into a smooth 

 and somewhat triangular plain surface, 

 upon which we occasionally lean. That na- 

 ture designed this for an occasional resting 

 place, is to be inferred from the coarse tex- 

 ture of the skin which covers it, which is 

 similar to that placed over the lower part 

 of the knee pan. 



The form of the corresponding articular 

 surfaces of the bone of the arm and ulna, 

 freely admits an extensive motion forwards 

 and backwards, and absolutely prevents any 

 other. The bone of the arm has a groove 

 formed in it, with lateral risings, and the 

 ulna has a middle projection with lateral 

 depressions. This groove making a kind 

 of hinge for the ulna to move on, is 

 formed obliquely, its upper part inclining 

 towards the body. When, therefore, we 

 bend the elbow, the fore-arm does not come 

 in opposition to the arm, but carries the 

 hand to the trunk of the body. When we 



