38 TRANSACTIONS OF THE TEXAS ACADEMY OF SCIENCE. 
and especially be trained to work at all times absolutely under brain 
control. 
The leverage of motion in the horse rests almost solely in the quar¬ 
ters, front and rear. Front leverage is perhaps of lesser moment, from 
the fact that main propelling power comes from rear development; 
but the trotting leverage in front is still of great importance, since by 
it alone we may determine reach and stroke, or smoothness of the 
stride. From a mechanical point of view the leverage in front presents 
an interesting double or compound lever, lifting of the knee being due 
to a lever of the third class, where the power acts between the fulcrum 
and resistance ; while the bending of the knee, or flexure of the cannon 
on the fore-arm, shows a lever of the same class, combined with pulley 
action of the tendons at the knee. If the fore-arm bone—the radius— 
be long, the lifting power of the muscles acting on the elbow as a ful¬ 
crum meets a greater weight resistance at the knee, the motion must 
