INFECTIOUS DISEASES. 523 



Old, cold, damp, foul, undean, and badly drained and ventilated 

 stables allow rapid dissemination 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. Prof. Dieckerhoff 

 found that the contagion of influenza was readily diffusible through- 

 out an entire stable and through any opening to other buildings, but 

 he also found that the contagion of infectious pneumonia is not trans- 

 missible at any great distance, nor is it very diffusible in the atmos- 

 phere. A brick wall 8 feet in height served, in one instance, to pre- 

 vent 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 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 delevop 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 secounds. The heart, 

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

 beating violently and tumultuously, as 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 dis- 

 tinguishable 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 

 directly behind the shoulder on each side of the chest. In some cases 

 the evidence of lung lesion can be detected only over the trachea. 



