AS TO SOUNDNESS. 119 
almost always in the epiphysal cartilage at the lower 
end of the femur in young men and women at a time 
.--according to anatomical text-books—when the epi- 
_physal cartilage is being converted into bone (Gray 
gives it at the twentieth year). We could easily multiply 
these examples, but you will already have learned the 
fact as one of the fundamental principles in physiology- 
Then if you find that these bones have little movement 
ong on the other, and have a tendency to become con- 
solidated, as -has been abundantly proved; and that 
during the process of consolidation the functional 
‘activity of their nutrient parts is intensified, and that 
under full functional activity a part is soon thrown into 
a‘state of disease,—I say, if you grant all this, why need 
we look for “concussion” acting upon healthy bones 
as the cause of spavin, as is usually done? You will 
perhaps have heard of the theory that spavin is produced 
by the concussion to which these parts are subjected 
when the horse sets his foot down, and that it occurs 
on thé ‘inner rather than on the outer side, because the 
‘dinner side is more under the centre of gravity. Now 
this is just nonsense. Look at any hock, and you will 
find that the direction of weight is from qw7thin outwards, 
and not, from without inwards. This is evident to all 
who examine the hip joint, also direction of the articular 
~ surface of the astragalus ; but most evident of all when 
“you watch a ‘horse that is either standing or moving. 
Gentlemen, spavin is caused by concussion, but it is 
_ the concussion of extreme flexion ; and this is why we find 
