INFECTIOUS DISEASES. 511 



great loss among the war horses of Rome and the surrounding dis- 

 trict. Later, in 1648, an epizootic of this disease visited Germany 

 and spread to other parts of Europe. In J711, 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 1732, 

 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 



