90 ON THE NAVICULAR DISEASE AND NEUROTOMY. 
therefore entitled to apply the reasoning I have adopted to it. It 
is only by viewing it in this light that we are enabled to account 
for all the phenomena which occur. In depriving the foot of its 
nervous communication with the rest of the body, we at the same 
time deprive it of its nervous, its vital energy; and we have then 
nothing to trust to but the exquisite mechanism and physical 
strength of the materials ; and we know that, however beautiful 
the parts of an animal body may be formed and arranged, its 
power resides in its vitality. The body is only the machine by 
which the animating spirits operate; the nerves are the wires 
which convey its commands and its powers to the individual parts. 
Such being the case, need we wonder that, deprived of such in¬ 
fluence, we find it soon gives way ? Nay, it has even been 
proved, that these parts, in otherwise a sound and healthy con- 
dition, are unable to withstand the friction and strain which 
exists. 
Mr. Castley has informed me, that in one instance, as an experi¬ 
ment, he divided the nerves of a horse above the pastern joint, in 
which the feet were sound, and that the flexor perforans some 
months after gave way; thus showing, that, when the vital power 
is destroyed or exhausted, the parts of a living body are acted 
upon like other machinery (it must be observed, however, that 
a horse witli long pasterns was selected for the experiment). I am 
therefore inclined to think that the nervous energy, with increased 
action of the Jiexorperforatus, has a greater influence in preserving 
the perforans tendon from being destroyed prior to the operation, 
than any controul the animal can possibly exert over the extensor 
muscles. 
If the extensor pedis is in a state of contraction, it must, of 
course, extend the foot, and the action of the extensor suffraginis 
will assist it; while the relaxation of the flexor perforans muscle 
will not relieve the navicular bursa, because the powerful liga¬ 
ment arising from the posterior of the os magnum of the carpus, 
and inserted principally into the perforans tendon (the corrected 
anatomy and diseases of which have been so strangely overlooked 
by British veterinarians), will, while the extensors are in action, 
keep the tendon of the perforans so much upon the stretch, that 
the navicular bone must be pressed upon and supported by it; 
but if the extensors are relaxed, and the limb is acted upon by 
the flexor perforatus, we at once see why by its increased action, 
and the remaining nervous energy of the part of the perforans, 
the tendon does not give way previously to the operation. 
