500 DISEASES OF THE HOESE. 



drinking water in troughs and even running water may hold the virus 

 and be a means of its communication to other animals, even at a 

 distance. The studies of Dieckerhoff, in 1881, in regard to the con- 

 tagion of influenza were especially interesting. He found that dur- 

 ing a local enzootic, produced by the introduction of horses suffering 

 from influenza into an extensive stable otherwise perfectly healthy, 

 the infection took place in what at first seemed to be a most irregular 

 manner, but which was shown later to be dependent on the ventilation 

 and currents of air through the various buildings. His experiments 

 showed that the virus of influenza is excessively diffusible, and that it 

 will spread rapidly to the roof of a building and pass by the apertures 

 of ventilation to others in the neighborhood. The writer has seen 

 cases that have appeared to spread through a brick wall and attack 

 animals on the opposite side before others even in the same stable 

 were affected. Brick walls, old woodwork, and the dirt which is too 

 frequently left about the feed boxes of a horse stall will all hold 

 the contagion for some days, if not weeks, and communicate it to 

 susceptible animals when placed in the same locality. A four-year- 

 old colt, belonging to the writer, stood at the open door of a stable 

 where two cases of influenza had developed the day before, fully 40 

 feet from the stall, for about ten minutes on two successive mornings, 

 and in six days developed the disease. On the morning when the 

 trouble in the colt was recognized it stood in an infirmary with a 

 dozen horses being treated for various diseases, but was immediately 

 isolated; within one week two-thirds of the other horses had con- 

 tracted the disease. 



Symptoms. — After the exposure of a susceptible horse to infection 

 a period of incubation of from four to seven days elapses, during 

 which the animal seems in perfect health, before any sjmiptom is 

 visible. When the symptoms of influenza develop they may be in- 

 tense or they may be so moderate as to occasion but little alarm, but 

 the latter condition frequently exposes the animal to use and to the 

 danger of the exciting causes of complications which would not have 

 happened had the animal been left quietly in its stall in place of 

 being worked or driven out to show to prospective purchasers. The 

 disease may run a simple course as a specific fever, with alterations 

 only of the blood, or it may become at any period complicated by 

 local inflammatory troubles, the gravity of which is augmented by 

 developing in an animal with an impoverished blood and already 

 irritated and rapid circulation and defective nutritive and reparative 

 functions. 



The first symptoms are those of a rapidly developing fever, which 



becomes intense within a very short period. The animal becomes 



dejected and inattentive to surrounding objects; stands with its head 



down, and not back on the halter as in serious lung diseases. It has 



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