EQUINE CONTAGIOUS PLEURO-PNEUMONIA 449 
media from the other organs (liver, spleen, and kidney) remained clear. The strep- 
tococci isolated from the different cases were identical in their morphology, cultural 
manifestations and pathogenesis. A microscopic study of the lungs from the different 
horses showed streptococci singly, in pairs and occasionally in short chains. Distinct 
capsules were not observed. In bouillon cultures, however, they appeared in long 
chains, leaving the liquid clear, as described by Schutz. 
Recent investigations indicate that the etiological factor will pass 
through the Berkefeld filter. Gaffky and Lthrs found that it was 
present in the smaller bronchioles and that it was forced out through 
the nose by coughing. They found that it lost its virulence soon 
after being expelled from the infected animal. It is spread by infected 
animals as soon as a rise of temperature begins. Natural infection 
usually takes place by direct contact. The disease has not been trans- 
mitted to horses by insects. According to Gaffky and Lihrs the virus 
is located in the bronchi. They conclude as follows: 
The disease as a rule is transmitted only from horse to horse. It 
is carried from animal to animal by the inhalation of drops of infected 
material which are expelled from a sick animal when coughing or 
sneezing. 
The virus is not found in the nasal discharge but it lies deep in the 
bronchi and is forced out through the nose by forcible coughing and 
sneezing and therefore renders the sick animal dangerous. 
The virus soon dies after being expelled from the sick animal. 
After 24 hours it has been found occasionally in the straw con- 
taminated by sick animals. 
An infected animal can spread the disease during the beginning of 
an attack or as soon as a rise of temperature is noted. 
The period of incubation is generally given as varying from one to 
fourteen days. According to Gaffky the period of incubation varies 
from 16 to 42 days. 
Symptoms. The symptoms vary to a marked degree. The first 
symptoms usually suggest croupous pneumonia. When pneumonia 
develops early in its course, the disease may appear suddenly; and in 
addition to the elevation of temperature there is a cough with difficult 
breathing. In those cases where the symptoms are restricted to those 
of a general infection the temperature drops to the normal in a few 
days. Often the symptoms differ from those of fibrinous pneumonia 
by the absence of distinct evidences of local lesions which are found 
in that disease. The first regular symptom is a rapidly rising tem- 
perature, frequently accompanied by a chill. The pulse rate is 
