AN ESSAY ON CHRONIC POUOTROCHOLITIS. 413 
very suddenly. An evident lameness succeeds to violent exer- 
tions ; to a hard and hasty course ; to leaps, & c. But in by far 
the majority of cases it developes itself insensibly, and its progress 
is so slow, that the commencement of the affection generally passes 
unperceived. The position of the limbs in the stable furnish the 
first indications of its existence. While the healthy leg, rested 
firmly on the ground, maintains its perpendicular direction, the 
diseased limb escapes as far as possible from bearing its share of 
the weight; it is held forward, extended from the body, and placed 
in such a position as keeps it half way between extension and 
flexion. This intermediate state is in some measure observable at 
all the joints; the knee and fetlock are advanced slightly forward. 
From time to time this position undergoes other variations, but 
the animal never rests upon the affected limb without great care 
and precaution, and avoids or diminishes the pressure of the heels 
on the ground. When led or mounted, either walking or trotting, 
in a confined space, the horse spares his heels in particular on hard 
ground ; the extension of the articulations, especially to those of 
the body, is net complete at the moment the foot treads the ground. 
These abnormal movements are, however, scarcely perceptible to 
those who have not made the subject their special study. The 
rider, endowed with that instinctive feeling which enables him to 
detect the slightest defect in the paces, perceives, after a sufficiently 
long ride, that there is something extraordinary, something irre- 
gular in the movement; but he attributes it to the idleness or dis- 
like to work of his steed, and he has recourse to the spur and the 
bit, or to the whip, in order to excite more action in the hind- 
quarters ; the anterior extremities, in consequence, become more 
free, the progression is improved, and he believes he has formed a 
correct opinion. 
This doubtful and obscure state may be prolonged for weeks 
and months before an unequivocal lameness, perceptible to every 
body, becomes suddenly or gradually manifest. 
The following are the characteristic signs of the lameness : — 
The horse, when put in motion, does not raise the diseased limb 
so high as the one on the opposite side, which we will suppose 
to be perfectly sound ; he does not throw it out so far ; the print 
of the foot is found nearer to the body, and a little outwards ; at 
each tread the joints are not thoroughly extended ; the carpus is 
but slightly flexed ; the pastern bones have less tendency to the 
oblique direction, approaching more to the perpendicular. 
Although the whole of the plantar surface of the hoof touches 
the ground, the chief part of the weight of the body is thrown 
upon the toe, in consequence of the limb being but imperfectly 
extended. These phenomena become more apparent when the 
