314 
W. L. WILLIAMS. 
breaks; in some the mortality falls to one per cent, or below, 
and the loss amounts practically to the loss of use of patient 
for three or four weeks’ trouble and expense of treatment, 
etc., while in other cases the mortality mounts up to thirty 
per cent, or over. Seasons, heat and cold or age of animal 
appear to exert no influence on the mortality, but damp, 
changeable weather, which would naturally predispose tc; 
chest diseases, aggravate these complications. Thinness ol 
flesh seems without prejudice, but excessive fatness, with 
high feed and scant exercise at date of invasion, is exceeding¬ 
ly baneful. Ordinary working animals, if promptly rested 
when attacked, withstand the disease best. On an average 
the mortality in the country and small cities may be placec 
at five per cent, or less with safety. In large cities with 
crowded stables it is evidently greater, Dieckerhoff estima 
ting the mortality at fifteen per cent, in Berlin, while Fried 
berger and Frohner place the mortality at twenty per cent 
to naught per cent.—usually at three and eight per cent. At 
all events, it may be said to be the most fatal of the class o 
diseases of the horse generally grouped together as having the 
type of influenza. 
The period of incubation is not accurately determined, anc 
is certainly not uniform. I have seen the disease appear a: 
early as nine days, and as late as twenty days after exposure 
What contact is necessary for transmission is also unknown 
most cases being evidently due to intimate associations o 
healthy with diseased animals. Quite frequently in larg( 
stables an animal several stalls distant from the diseased onf 
will contract the malady, while those in intervening stalls re 
main free. Usually part of the horses in a stable escape 
sometimes as high as thirty to fifty per cent, resist its en 
croachments. Like most epizootic diseases it generally di 
minishes in virulence after existing for several months in ; 
locality and finally disappears. It spreads slowly, and cai 
probably be transmitted by the air for a short distance only 
In one case two draft stallions, occupying a stable by them 
selves, contracted the malady, and both died, while the othe 
horses of the farm, scarcely a hundred yards distant, remained 
