34 Williams, Fisher, and Udall: The Spavin Group. 
osteo-porosis presented at the clinic of the New York State 
Veterinary College, while spavin and its allies easily takes first 
place numerically among all diseases -of the horse, whether 
medical or surgical, contagious or sporadic, but those animals 
presented because of this malady by no means represents the 
sum total of animals presented with it for other ailments. Nor- 
mally, only those cases which are lame are presented because 
of the affection, but probably not more than twenty per cent. of 
the affected are lame, a large proportion of them apparently 
escaping lameness throughout their lives. We must leave the 
identification of this malady for further study, with the hope 
that the important group of diseases, expressed chiefly by a 
rarefying ostitis or porous and softened condition of the bones, 
possibly accompanied in all forms by phosphaturia, either be 
definitely identified as a single disorder or ‘clearly separated 
from each other in a manner as to permit of a safe differential 
diagnosis. 
InFecTION. Over and above all causes suggested stands 
the question of infection, one which is quite unanswerable from 
the data at hand. 
Clinically such an explanation is not rendered impossible, 
and some investigators claim an infection as the fundamental 
cause. 
FACTORS IN THE LOCALIZATION OF THE LESIONS. 
If the disease, as we have already ventured to say, is funda- 
mentally a constitutional and not a local one, it remains for 
us to consider the causes for the concentration in oné or more 
small areas of the visible indications of the malady as expressed 
in exostosis, lameness, or other abnormality. 
In discussing the causes of the malady, we have. taken 
_ occasion to state that in our opinion many of the alleged chief 
causes were contributory or modifying rather than, essential, 
since in our view they tend to determine the location of the 
pronounced symptoms of the disease, after the essential consti- 
tutional disturbances have become established either visibly or 
invisibly. We believe also that mechanical insult, either direct 
or indirect, may act as the sole means of developing the visible 
signs of the disease, which might otherwise disappear by reso- 
lution. We are not in a position to deny the possibility of 
