VARIOLA EQUINA. 
253 
fourth day a single vesicle forms, containing clear lymph, which 
enlarges till about the seventh day; it attains a diameter of an 
eighth of an inch and gradually becomes opaque. About the 
tenth day it is yellow, and the surrounding tissues are swollen 
and red. It now gradually begins to desiccate, beginning in 
the centre; the scab thickens, dries, and becomes of dark brown 
colour, and about the seventh day it is thrown off, leaving 
a scar similar in every respect to that seen from vaccination. 
With regard to the causes of this disease, it may be diffi¬ 
cult to account for it. During a residence extending over 
seventeen years in Canada, I have only seen it twice, viz: in 
1877 and during the present winter. There can be no doubt 
that it is dependent on some peculiar atmospheric condition, 
sudden changes of weather, such as have recently prevailed 
here, or other causes purely local. That it is contagious 
cannot be doubted, and that it is infectious I am also in¬ 
clined to believe, but neither contagion nor infection form 
marked features in the disease. For instance, in the College 
Hospital, which for several weeks back has been full of 
variolous patients, my own horses and half a dozen others 
have not presented any symptoms of the disease. True, the 
patients are in loose boxes, and dressed by different persons 
from the healthy horses. Again, in an establishment of 
nearly 200 horses only three or four cases have occurred, 
while in some stables of two or three horses, all have become 
affected. That the disease can be carried to a distance and 
become epizootic I do not believe. Thus, for instance, I do 
not believe that a horse suffering from variola taken to, say 
Boston, or New York, would introduce the disease to these 
cities as an epizootic, unless the climatic and atmospheric 
conditions necessary for its existence and spreading existed 
there, which is very improbable; consequently no apprehension 
need be felt on account of it. At most it is merely a tempo¬ 
rary inconvenience, necessitating, in the majority of cases, 
cessation from work for about three weeks, and if allowed to 
run its regular course unattended by any injurious results. 
Injudicious doctoring, or keeping the animal at work, may 
produce sores of the heels affecting the deep tissues, which 
are sometimes difficult to heal. 
I may further add that, whatever the cause has been, it 
seems to have exhausted itself, as the disease is rapidly 
disappearing. Veryjfew new cases are occurring, and most 
of those labouring under it are returning to work. 
D. McEachran, F.R.C.V.S., 
Inspector of Stock for the Dominion Government. 
Montreal Veterinary College, February 28, 1880. 
LIII. 18 
