viil INTRODUCTION 
of $6,605,000; 2,906,000 ducks valued at $1,567,000; 4,431,000 
geese valued at $3,194,000; 1,765,000 guinea fowls valued at 
$613,000; 2,730,000 pigeons with a value of $762,000; 6,458 pea 
fowls estimated at $18,000; and 5,361 ostriches valued at $1,- 
696,000. In 1915, this country imported ostrich and other feathers 
to the value of $2,500,000. Besides, there is a large business in 
song and other birds maintained as pets. 
In certain localities, the raising of one or more species of poultry 
constitutes the essential occupation of many of the people. The pro- 
ductivity of domestic fowls is greater than that of any other species 
of animals in proportion to their value. The price of the annual 
products from a flock of ducks, hens or turkeys may be many times 
larger than the cost of the original flock. 
There is no other form of animal life that suffers more from the 
ravages of disease than fowls. The losses from the general maladies 
are heavy and those from the infectious ones are sometimes appal- 
ling. Various estimates have been made of the annual losses occa- 
sioned by these causes. They vary from 10 to 30 per cent. Hens 
in particular suffer from a wide range of diseases and parasitisms. 
Some of these are veritable plagues and at times are the cause of 
serious losses. In 1903, while studying poultry diseases in a lo- 
cality where eggs and chickens were the chief articles of commerce, 
it was not unusual to learn of individual losses ranging from a few 
hundred to several thousand dollars due to roup or diphtheria. 
Other large flocks were decimated by tuberculosis. While it is easy 
to understand that heavy losses may occur in localities where fowls 
are kept in large numbers, it should be recognized that they are 
proportionately heavy in smaller flocks. In such circumstances, the 
death of a few hens is often the cause of much privation if not actual 
suffering among their owners who are dependent upon the products 
of their fowls for the necessities of life. 
The general diseases of poultry present many points of interest, 
although they have received relatively little attention. The general 
pathology of the feathered tribes is not well understood. Little 
seems to be known of their tissue reactions to injury. Their resist- 
ance to ordinary wound infections differs strikingly from that of 
mammals. Pasteur suggested that this might be due to their higher 
body temperature. On the other hand, the infectious diseases and 
parasitisms have been more carefully studied. The findings of 
many valuable researches are recorded on the nature of the more 
serious ones. Certain of them, such as bacillary white diarrhea and 
