Fowl Typhoid and Fowl Cholera 
53 
On the same basis of reasoning, eliminating attempts to infect immunized 
birds, these experiment would show that 30 out of 100 birds are naturally 
immune to avian typhoid, or a figure fairly close to Salmon’s estimate. 
These figures compare favorably to the mortality index of outbreaks in the 
field as shown in Table IV, in which the flock mortality before vaccination 
was 26 per cent; after vaccination 3.8 per cent; with a total mortality of 29 
per cent, which would give the per cent of birds naturally immune up to the 
time of vaccination of 74 per cent. 
teHennepe (33) is inclined to consider the disease as very acute, and sets 
the duration from one-half day up to five days, with chronic cases occurring 
rarely, such cases being important from a pathological and anatomical stand¬ 
point. teHennepe’s conception would tend to concentrate the stages of the 
disease as outlined above. 
Truche and Staub (32) held that the duration of the disease is variable but 
generally runs its course in from 2 to 3 days, which would have the same 
effect in concentrating the periods as teHennepe’s conception. 
HEAT ELIMINATION IN FEBRILE DISEASES 
The different tissues of the bird s body eliminate heat in amounts corre¬ 
sponding almost precisely with the intensity of their metabolism in health, 
but this equilibrium may be disturbed in disease. The body temperature 
deviation due to age, sex, exercise, season, climate or feathers rarely under 
normal conditions amounts to more than one or two degrees, and is temporary 
FIG ' o 2 a°; 75 k ^™ GRApHIC tracing of normal respiration of bird, and 
SAME BIRD IN EARLY AND IN ADVANCED STAGES OF FOWL TYPHOID 
in nature. Increased body temperatures may also be caused by a rise of out¬ 
side temperature (1). This change is usually associated with increased fre¬ 
quency of heart action and with respiration, fatigue and possible loss of 
consciousness, and death may result in a short time. The diurnal variation 
of the normal temperatuere of a fowl ranges from 104.5 degrees F. between 
midnight and 3 a. m., to 107.3 degrees F. between 12 mid-day and 5 p. m. 
The temperature of the larger birds as turkeys and geese are slightly lower 
than that of hens, while the temperature of the smaller birds, as pigeons, is 
slightly higher (14). 
Hyperthermy, or the condition known as fever, is represented by a complex 
of symptoms of which a decided and lasting elevation of body temperature is 
characteristic. This condition is not due to food, exerciste, or environmental 
temperature, but is usually caused by the breaking down of the functioning 
