INFLUENZA. 499 



day, 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 epizootics 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 gastro-enteritis. 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 west- 

 ward to California. It is now a permanent disease in our large cities, 

 selecting 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 

 exposed to its contagion. 



Etiology. As one attack is self-protective, numbers of old horses, 

 having had an earlier attack, are not capable of contracting it again ; 

 but, aside from this, young horses, especially those about four or five 

 years of age, are much more predisposed to be attacked, while the 

 older ones, even if they have not had the disease, are less liable to it. 

 Again, the former age is that in which the horse is brought from the 

 farm, where it has been free from the risk of exposure, and is sold to 

 pass through the stables of the country taverns, the dirty, infected 

 railway cars, and the foul stockyards and damp stables of dealers in 

 our large cities. Want of training is a predisposing cause. Overfed, 

 fat, young horses which have just come through the sales stables are 

 much more susceptible to contagion than the same horses are after a 

 few months of steady work. 



Pilger, in 1805, was the first to recognize infection as the direct 

 cause of the disease. Roll and others studied the contagiousness of 

 influenza, and, finding it so much more virulent and permanent in 

 old stables than elsewhere, classed it as a " stall miasm." The at- 

 mosphere is the most common carrier of the infection from sick ani- 

 mals to healthy ones, and through it may be carried for a considerable 

 distance. The contagion will remain in the straw bedding and 

 droppings of the animal and in the feed in an infected stable for a 

 considerable time, and if these are removed to other localities it may 

 be carried in them. It may be carried in the clothing of those who 

 have been in attendance on horses suffering from the disease. The 



