DISEASES OF HORSES 49 



caused it for a long time to be confounded with influenza, with which 

 at certain periods it certainly has a strong analogy of symptoms, but 

 from which, as from sporadic pneumonia, it can be separated very 

 readily if the case can be followed throughout its whole course. 

 Edematous pneumonia is a specific inflammation of the lungs. It 

 causes a profound sedation of the nervous system, which may be so 

 great as to cause death. It is sometimes attended by pleurisy, inflam- 

 mation of the heart, or septic complications which also prove fatal. 



Etiology. While, as an infectious disease, its original cause ia 

 due to a specific virus, there are many predisposing causes which act 

 as important factors in aiding in its development. Such causes are 

 any influences that lessen the general vigor. Old, cold, damp, foul, 

 unclean, and badly drained and ventilated stables allow rapid dis- 

 semination of the disease to other horses in the same stable and act as 

 rich reservoirs for preserving the contagion, which may be retained 

 for over a year. The virus is but moderately volatile, and in a stable 

 seems rather to follow the lines of the walls and irregular courses than 

 the direct currents of air and the tracts of ventilation. A brick wall 

 8 feet in height served, in one instance, to prevent the infection of 

 other animals placed on the opposite side from a horse ill with the 

 disease, while others placed on the same side and separated from the 

 focus of contagion only by open bars in the stall were infected and 

 developed the disease in its typical form. 



Symptoms. The symptoms differ slightly from those of a frank, 

 fibrinous pneumonia, but not so much by the introduction of new 

 symptoms as by the want of or absence of the distinct evidences of 

 local lesions which are found in the latter disease. All of the pneu- 

 monias throughout the whole course of the trouble are less marked 

 and less clearly defined. 



The symptoms may develop slowly or rapidly. If slowly, there 

 is fever and the animal gives a rare cough which resembles that of a 

 heavy horse affected with a slight chronic bronchitis; it becomes 

 somewhat dejected and dull, at times somnolent, and has a dimin- 

 ished appetite. This condition lasts for several days, or the disease 

 may begin with high fever, and the symptoms described below are 

 severe and develop in rapid sequence. The respiration increases to 

 24, 30, or 36 to the minute, and a small, running, soft pulse attains 

 a rhythm of 50, 70, or even more beats in the sixty seconds. The 

 heart, however, contrary to the debilitated condition of the pulse, is 

 found beating violently and tumultuously, like it does in anthrax and 

 septic intoxication. The mucous membranes of the eyes and mouth 

 and of the genital organs are found somewhat edematous, and they 

 rapidly assume a dirty, saffron color, at times approaching an ocher, 

 but distinguishable from the similar coloration in influenza by the 

 want of the luster belonging to the latter and by the muddy, dull tint, 

 which is characteristic throughout the disease. 



Suddenly, without the preliminary rales which precede grave 

 lesions of the lungs in other diseases, the blowing murmur of pneu- 

 monia is heard over a variable area of the chest, usually, however, 

 much more distinctly over the trachea at the base of the neck and 



