INFECTIOUS DISEASES. 523 
Old, cold, damp, foul, unclean, 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. 
