INTRODUCTION 
The statement is accepted that diseases are the greatest hindrance 
to the development of animal and poultry husbandry. Measures 
for the prevention, successful treatment or control of these maladies 
must come from those who understand their nature. It is grati- 
fying, therefore, that veterinarians, and others interested in the 
subject, are to have access to a volume dealing with the diseases 
of poultry, prepared by men of long experience in the study of the 
phenomena of disease. Likewise, poultry raisers will appreciate 
a treatise setting forth the known facts concerning the maladies 
which sooner or later may affect their flocks. A book of this kind 
will be of indispensable value in eliminating many of the miscon- 
ceptions regarding the diseases of poultry and in pointing out the 
things that are known and the precautions that must be observed in 
maintaining healthy flocks. 
The extent of the poultry industry in the United States is little 
appreciated by veterinarians. There is no other species in the 
animal kingdom that contributes to the material support of so large 
a number of people as the domesticated fowl. In addition turkeys, 
geese, ducks and pigeons are significant factors in food production 
while the ostrich and other birds play an important part in orna- 
mentation. In the Hartz Mountains, the raising of canary birds for 
the amusement and entertainment of people is an important in- 
dustry. 
The barnyard fowl plays a large part in the food supply of the 
country. The extent of the poultry business can be approximated 
from the fact that in 1910 there were 5,578,525 farms in the United 
States that reported a total of 280,350,000 fowls with a value of 
$140,205,000. With the prices at the present time, their value 
would be treble that of 1910. In 1915, the United States exported 
20,784,000 dozen eggs but it imported over 3,000,000 dozen and 
over 8,000,000 pounds of egg yolks and frozen eggs. These figures 
indicate the large number of people who are financially interested 
in the poultry business. 
The raising of turkeys and other species is also significant. In 
1910 there were in the United States 3,688,000 turkeys with a value 
vill 
