CONTAGIOUS PLEURO-PNEUMONIA. 
303 
nade by myself by inoculating subcutaneously with warm 
>lood. The pulmonary and pleural exudates are generally 
redited with being richest in the essential germs, but the 
:onstant and severe engorgement of the liver would suggest 
hat organ also as a rich breeding-ground. 
The disease exists most frequently in large city stables, 
ixtensive breeding studs, military establishments, and other 
daces where there are considerable aggregations of horses. 
n our great cities the disease becomes permanently estab- 
ished and domiciled, the constant influx of country horses, 
lot yet rendered immune, serving to maintain its uninter¬ 
rupted prevalence. Friedberger and Frohner hold that it 
)ccurs mainly in horses aged five and ten years, but we can 
)nly see in this the age at which horses are generally sent to 
he cities, and largely for the first time exposed. In our ex- 
Derience in an almost purely breeding district we observed 
nore cases in animals below five years than over, young foals 
suffering as constantly as other ages. We are led to believe, 
.herefore, that age has no influence in the dissemination of 
;he disease. It attacks with equal certainty all breeds, and 
it all seasons of the year, but, like many contagious diseases, 
dose confinement in crowded, ill ventilated stables, excessive 
'eeding and extremes of labor or inactivity serve to increase 
the facilities for spreading and markedly heighten the mor¬ 
tality. 
While bacteriological investigations as to the conta¬ 
gious nature of this disease are meager, we have clinical evi¬ 
dence of the highest order of its purely specific character. In 
large cities where, in common with this malady, cellulitis, in¬ 
fluenza in its restricted sense, strangles and perhaps other 
specific equine diseases are permanently rooted, two or more 
of them not infrequently co-exist in the same stable, and even 
in the same animal, leading to confusion, and the grouping 
together by the various veterinary writers (mostly city prac¬ 
titioners) of a number of wholly distinct contagious diseases 
under the name of influenza. In smaller cities, however, and 
especially in breeding areas where extensive studs are kept 
well isolated from other animals, such maladies can be seen 
