Williams, Fisher, and Udall: The Spavin Group. 45 
In other cases the constitutional changes are so rapid and 
severe that the animal quickly loses condition, is listless, disin- 
clined to move, becomes greatly emaciated, spontaneous frac- 
tures occur or the case otherwise becomes hopeless and the animal 
is destroyed. 
The vast majority of cases pursue courses between these 
extremes. Many young animals develop multiple exostoses with- 
out notable lameness, anchyloses occur in some of the smaller 
joints, the patient recovers its general vigor and goes through 
life doing satisfactory labor without lameness. 
Many other cases, especially in young animals, are lame for 
a time, but if the joint be of limited motion, anchylosis may 
occur after some months or even years and the lameness dis- 
appear. Subsequent to anchylosis the lameness may recur in 
the affected joint at any time during the patient’s life, due 
either to a return of the disease process or to an accidental dis- 
turbance of an imperfect anchylosis. Sixty to seventy-five per 
cent. of spavin and ringbone lameness in young animals end in 
recovery by anchylosis if early attention be given. 
In the residue of these cases and in sixty to seventy-five per 
cent: of aged horses that become affected, the disease in these 
joints resists treatment and remains permanent, seriously dimin- 
ishing and frequently destroying the value of the animal. The 
character of the articulation modifies greatly the prognosis. 
When the disease affects the stifle (gonitis), a colt may recover, 
but the collection of synovia in the femoro-patellar capsule usually 
floats the patella outward, causing it to pass over the external 
femoral condyle producing “floating” luxation, ending in a 
failure of the external condyle to develop, thus destroying the 
trochlea and even if the disease processes abate, the patella slips 
out and in at each step and the animal is worthless. This result 
is well shown in Figs. VIII and IX. Anchylosis being barred 
in such articulations, when important changes have occurred in 
the joint, the lameness becomes permanent and disabling. 
In some cases of chronic navicular disease, it is believed that 
the flexor tendon and bone become anchylosed and alleviate or 
stop the lameness. In one very lame dissecting subject, we found 
firm anchylosis between the bone and tendon. 
Anchylosis cannot well occur in important joints, and when 
it does, that in itself renders the animal useless. Anchyloses of 
the vertebrz, especially in the lumbar region, are not rare; when 
