44 Williams, Fisher, and Udall: The Spavin Group. 
a modification of the lameness by inducing local anesthesia of 
the hock and thus exclude the spavin. 
- Spavin and ringbone exostoses frequently occur together and 
are difficult to differentiate. The spavin test is uncertain as the 
flexion usually involves violence to both parts, though the com- 
pression on the ringbone may be reduced to a minimum by 
exerting the force upon the metatarsus instead of the toe. 
If one of the exostoses is old and the other recent, the lame- 
ness may be fairly attributed to the latter: 
The best method of differentiation is local anzesthetization 
of the plantar nerves. 
In the fore foot we find difficulty in differentiating between 
ringbone, sidebone, and navicular disease, and in some cases we 
meet with compound lameness, all three being present, as is 
shown in Figs. XVIII and XXI. The presence of ringbone pro- 
hibits, especially if it is low, the detection of navicular lameness, as 
any test which we may be able to apply to the one will act very 
similarly on the other. The sidebones frequently extend up so 
high as to cover over or become continuous with ringbones in 
which case we are powerless during the life of the animal to 
differentiate. The common presence of sidebones and ring- 
bones in draft horses with navicular disease prevents the diag- 
nosis of the latter and leads to the opinion that it does not occur 
in draft animals. When but one form of exostosis is present and 
we'can detect no navicular disease, we may assume its absence, 
but it is not safe to base a prognosis upon such assumption. 
In the absence of exostosis, navicular disease is fairly easily 
diagnosed.’ It must always be remembered in differential diag- 
nosis that a horse limping to-day from a slight ringbone may be 
lame to-morrow from navicular disease, conditions which give 
abundant room for professional friction when different veteri- 
narians examining a horse at close intervals clash in diagnosis. 
Each may be correct. 
COURSE AND TERMINATION. 
As in other diseases resolution may, and frequently does occur. 
When recognized early in its course ere irrecoverable lesions 
have occurred, the causes removed and prompt measures taken 
to correct the local and general disturbances, recovery may be 
complete and permanent. | ; 
