SPONTANEOUS LUXATION OF THE PATELLA. 145 
chanical injury ; but those described by M. Conte, as of a case of 
cramp, are precisely what would have been presented had it been 
dislocation of the patella, and which, I think, justifies me in pre- 
mising that such might have been the case, and in making these 
few observations thereon. 
If a young practitioner, who had read the description of this 
case of cramp, was required to attend an animal presenting these 
symptoms, he might be thrown off his guard and consider it as 
cramp ; when, should it eventually prove luxation of this bone, the 
discovery of it by himself, or another person subsequent to him 
having given his opinion on the case, would be very annoying. 
For an instance, compare Mr. Percivall’s relation of the symptoms 
of dislocation of the patella and M. Conte’s symptoms of cramp. 
Mr. Percivall states, “ that, in dislocation of the patella, there is 
stiffened protrusion of the whole limb backwards .” This / believe 
to be in consequence of the animal trying to move forward until 
this limb, in the order of progression, should advance, and that not 
being accomplished leaves the leg in this position, and so retained 
by the spasmodic action of the flexors. This is not always or neces- 
sarily the case, for I have noticed that, when the patient has been 
confined in a stall where he could not move forward, the limb has 
oftener been pointing outwardly, or directly under the animal, as if 
in the former case he had moved sideways, and in the latter made 
no motion after the occurrence, the stiffness of the limb always 
existing, and the foot never leaving the ground until the animal 
moves as far he can forward without advancing this limb. The 
foot then becomes suddenly flexed, and the limb remains from that 
time in the position described by Mr. Percivall, viz. “ the pastern 
and foot flexed to the utmost, quite incapable of being straightened, 
and trailed along the ground when the animal is made to move, 
with perceptible prominence and tenderness of the outer side of the 
stifle joint.” Then M. Conte’s case of cramp : “ the limbs fixed, 
almost immoveable; the muscles strongly contracted, prominent, 
and hard, the articulation of the fetlock joint alone being moved ; 
and considerable sensibility in the skin.” By this comparison it 
will be observed that these symptoms so far correspond in every 
particular as to be easily accounted for, were it concluded that this 
was a case of dislocation of the patella. The limb is immoveable, in 
consequence of the muscles that should advance it having lost 
their functional power, and by this rendering their antagonists 
spasmodic in their action, occasioning the secondary effect in which 
the muscles are rendered prominent and hard by extraordinary 
exertion of their contractile power, and thus producing cramp as a 
symptom. For although systrema is generally considered to arise 
from an excess of re-action, produced by the stimulus of too great 
VOL. XVIII. X 
