“INFECTIOUS DISEASES. §11 
great loss among the war horses of Rome and the surrounding dis- 
trict. Later, in 1648, an epizootic of this disease visited Germany 
aad spread to other parts of Europe. In 1711, under the name of 
“ epidemica equorum,” it followed the tracks of the great armies 
all over Europe, causing immense losses among the horses, while 
rinderpest was scourging the cattle of the same regions. The two 
diseases were confounded with each other, and were, by the scien- 
tists of the day, supposed to be allied to the typhus, which was a 
plague to the human race at the same time. We find the first advent 
of this disease to the British Islands in an epizootic among the 
horses of London and the southern counties of England in 1782, 
which is described by Gibson. In 1758 Robert Whytt recounts the 
devastation of the horses of the north of Scotland from the same 
trouble. Throughout the eighteenth century a number of epizo- 
otics occurred in Hanover and other portions of Germany and in 
France, which were renewed early in the present century, with 
complications of the intestinal tract, which obtained for it its name 
of gastroenteritis. In 1766 it first attacked the horses in North 
America, but is not described as again occurring in a severe form 
until 1870-1872, when it spread over the entire country, from Canada 
south to Ohio, and then eastward to the Atlantic and westward to 
California. It is now a permanent disease in our large cities, select- 
ing for the continuance of its virulence young or especially sus- 
ceptible horses which pass through the large and ill-ventilated and 
uncleaned stables of dealers, and assumes from time to time an en- 
zootic form, when from some reason its virulence increases. It as- 
sumes this form also when, from reasons of rural economy and com- 
merce, large numbers of young and more susceptible animals are ex- 
posed to its contagion. 
Etiology——The experiments of Dieckerhoff many years ago proved 
that the disease may be transmitted to healthy animals by intravenous 
injection of warm blood from affected horses. 
Further investigations revealed the fact that blood from affected 
horses, even when passed through porcelain filters, may transmit 
the disease, thereby proving that the causative agent belongs to the 
so-called filterable viruses. This has been further substantiated by 
Gaffky, who showed in his recent experiments that the disease may be 
transmitted with defibrinated as well as with filtered blood, in which 
cases the typical form of influenza developed in inoculated animals 
in from five to six days. These findings were also substantiated by 
Basset. Further observations have also proved that apparently re- 
covered animals may harbor the infection for a long time and still be 
capable of transmitting the disease. Such virus carriers are no doubt 
_responsible for numerous outbreaks of this disease when, in a locality 
