THE ' KNEE ' OF THE HORSE. 11 



nearly reach to the lower end of the radius, to which 

 it is fused so as practically to form a single bone. 

 The upper end is prolonged, flattened, and plays in 

 the groove at the lower end of the humerus, so that 

 no rotation is possible. The prolonged portion forms 

 the elbow of the horse (olecranon). 



In order to show this structure more clearly, the 

 joint is given on a much larger scale on page 12. Here 

 A represents the lower end of the humerus with its 

 double head and central groove ; c is the radius, 

 and c the ulna. The reader will here see how it is 

 fused into the radius, and how its flattened prolonga- 

 tion plays up and down in the groove. D is the 

 olecranon, or elbow. 



Descending still lower, we find the bones of the 

 wrist (carpus), or 'knee' as it is popularly called. 

 These are much the same as those of the human wrist, 

 except that they are simpler in structure. 



Now, however, we find a most radical change. 

 Compare the bones of the human hand with those of 

 the horse. No resemblance seems at first sight to 

 exist between them ; yet we know that, different as 

 they may seem, they are composed of the same 

 elements. In order to solve this problem we must 

 have recourse to geology and comparative anatomy. 



The former science shows us that the horse of the 

 present period is the last of a long series, extending 



