Williams, Fisher, and Udall: The Spavin Group. 29 
We have already pointed: out that shoeing cannot influence 
the whole group, but only a few members, and paved streets 
can scarcely occupy an essential place, or the disease could 
not be abundant in country places. In the vicinity of the New 
York State Veterinary College the disease among farm horses 
is so prevalent as to givé it the proportions of an enzodtic of 
serious import, but there are no paved roads to act as a causative 
factor. 
Ciimate. The effect of climate has not been well studied, 
but it is known that this group of affections have rather inter- 
esting geographical limitations, but whether this is due directly 
to the effect of the climate upon the horse, or whether it is 
rather indirect through the food and the necessity for stabling 
has not been definitely ascertained; but, so far as observed, 
its influence is indirect. The affection is most common in the 
eastern United States, and in the great cities of the middle states ; 
it is comparatively rare in the agricultural districts of the Mis- 
sissippi valley, and becomes more rare as the Rocky Mountains 
are approached, where over large areas it is practically unknown, 
to become more common again on the Pacific slope. 
Various explanations may be offered. The horse normally 
belongs to high, arid or semi-arid plateaus with dry soil and 
not very abundant vegetation of a high nutritive value and free 
from fungi, which conditions are attained in those regions where 
the disease is most rare. We must at the same time note that 
in these regions the horse enjoys the greatest liberty and is 
little confined in stables; it is, moreover, the newest part of 
our country. The senior contributor has noted an apparent 
increase of this malady in central Illinois as the country be- 
comes older and the soil and crops have undergone changes 
as the outcome of continued cultivation. 
Foop. A restricted diet constituting an unbalanced food 
ratio induces serious perversions of nutrition, among which 
we meet with experimental rhachitis, wherein a condition of. 
the bony skeleton is induced which is not distinguishable from 
the changes taking place in this group of lamenesses. Pigs fed 
upon an exclusive diet of corn meal and confined closely so 
as to limit them strictly to the diet given, soon succumb to 
tickets. A similar condition is seen in horses fed exclusively 
on bran. Hinebauch presented a highly interesting paper at 
our thirtieth annual meeting (Proceedings of U. S. V. M. A,, 
