102 DISEASES OF DOMESTICATED BIRDS 
fect may be termed a “ bird cough.” Prompt attention in such cases 
nearly always saves the life of the fowl. 
The disease spreads rapidly through a flock affecting a large per- 
centage of the birds and causing the death of a variable percentage 
according to the virulence 
of the virus. Young birds 
are especially susceptible, 
adults less so, and a few 
exhibit complete  resist- 
ance. 
Morbid anatomy. The 
external lesions have the 
appearance of wart-like 
growths prominently raised 
from the surface of the 
skin. The size may vary 
to a considerable degree 
according to location, or 
through combination of 
several nodules. General- 
ly they have a diameter of 
1% to % of an inch. 
These pox tumors occur 
chiefly on the unfeathered 
or lightly feathered por- 
tions of the body, and par- 
ticularly on the comb, wat- 
tles, eyelids and at the 
commissures of the beak. 
z ie ak They may also be found at 
Ta. 8. ead of a Plymouth Rock cock affected a 
with epithelioma contagiosum (bird pox). Bete the under surface 
(Klee) of the wings, particularly 
if there has been an abrasion or bruise at this point. They may be 
rarely observed around the vent. The nodules first appear as small 
whitish points which rapidly increase in size, reaching their maxi- 
mum size in four to six days. They form an integral part of the 
epithelium, being in reality an extrusion of enlarged epithelial cells. 
If the superficial scale of exudate is removed, the tumor will be seen 
to consist of whitish cylindrical masses arranged perpendicularly to 
the skin. The mass assumes a yellowish color which later changes 
to a dark brown or black as the tuberosity degenerates and develops 
