FOWL PLAGUE 85 
Exudate in the abdominal cavity is either serous or sero-fibrinous. 
The fibrin as a rule is in suspension in the serous fluid in the form 
of flakes, or is deposited loose on the peritoneum in the form of 
threads or sheets. 
The peritoneum is not inflamed but is smooth, shiny and trans- 
parent. Exudate occurs in the abdominal cavity in about a quarter 
of the cases. 
Exudate occurs in the pericardium in the form of a serous or 
sero-fibrinous fluid, which on opening of the pericardial sac often 
coagulates into a gelatinous mass. The presence of exudate in the 
pericardium occurs somewhat less often than in the abdominal 
cavity. 
A bluish red coloration of the comb occurs very often. There 
is nothing characteristic about it as compared with a number of 
other diseases. 
Some authors emphasize the significance of catarrh of the upper 
air passages and of the pharynx. They note the occurrence of 
viscid gray white mucus in the beak, throat and nasal cavity, but it 
is considered to be a normal secretion which remains in its place 
of production for some time before death. 
In wild ducks ‘dying of the nervous type it has been noted that 
autopsy reveals no characteristic gross changes. 
Diagnosis. The presence of hemorrhages in the proventriculus, 
the swelling of the kidneys and the severe injection of the blood 
vessels in the yolk capsules of the ovary, occasionally associated with 
the presence of hemorrhages, in birds dying of a pest-like disease, 
are most significant. The autopsy findings alone will not. always 
suffice for making a diagnosis. In some cases as in other infectious 
diseases, the lesions may be so slight as not to warrant drawing 
conclusions. A diagnosis of fowl plague can be established most 
certainly by successful transmission to a hen with absence of a 
causative agent recognizable in tissues or in cultures from the blood 
and organs. 
Differential diagnosis. Phosphorus poisoning causes lesions 
having the greatest similarity to those of fowl pest and also causes 
a high mortality. In general the hemorrhages in the proventriculus 
occurring in phosphorus poisoning extend deeper than in fowl pest, 
also in the poisoning, erosions occur in the hemorrhagic mucosa. 
In phosphorus poisoning there is also a marked inflammation of the 
upper part of the intestine. Notwithstanding the great similarity 
of the lesions the two conditions can be differentiated at autopsy by 
