AS TO SOUNDNESS. 113 
a big, flat, square hock, he means a hock having these 
qualities when it is not bent or flexed. ‘What is it that 
allows our point number ! to alter its relative position so 
much?. It is as your anatomy teaches you, the com- 
‘paratively small articular lower end of the tibia which 
glides over the large wide and deep articular surface of 
the astragalus. 
Just one other point to which I must draw your 
attention. I have told you that all the parts below the 
‘lower end of the tibia may be regarded as one structure ; 
‘the relative positions of thése parts are always the same, 
hence the articular surface of the astragalus always has 
the same relative position to the other structures, of 
which it forms a part—that is to say, it never looks more 
up or more down, more inside or more outside, without 
all its belongings altering their positions with it (except 
in the curby hock); so that it follows that when you 
have not a square hock our point number ? approaches 
point number * by the lower articular end of the tibia 
having glided more or less over the large articular surface 
of the astragalus, and it follows that the more it does so 
the nearer does the long axis of the tibia approach the 
parts beneath it at a right angle. 
In the next place, I wish you to notice what it is that 
‘gives size to the hock, or perhaps I ought rather to have 
said, gives it apparent size. Doubtless you will see that 
the apparent size depends upon the relative position 
of our point number * to point number 3, or in other 
words, if the articular lower end of the tibia be well 
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