DISEASES AND PESTS OF FOWLS 
aroused if birds gradually lose weight and 
die. If a bird that 
has gradually been 
getting thinner, goes 
lame, or loses the use 
of a wing, without ap- 
parent injury, the evi- 
dence that tuber- 
culosis is present is 
strong, but positive 
proof of its presence 
can be obtained only 
by post-mortem and 
microscopic examina- 
tion. This disease gen- 
erally attacks adult 
birds. 
Cause. The specific 
organism causing this 
disease, known as the 
Bacillus tuberculosis 
(Fig. 5), infects the 
liver (Fig. 24), the 
spleen (Fig. 24), and 
other organs, least fre- 
Fic. 24.—ORGANS AFFECTED BY 
TUBERCULOSIS AND BLACKHEAD 
a. Normal spleen. 
b. Tubercular spleen. 
c. Portion of tubercular liver. 
d, Blackhead liver of turkey for 
comparison with c. 
a and b after Edwards. 
gI 
