CAUSING ACUTE INFECTIONS. 
85 
way of the respiratory tract, and the symptoms of the 
disease manifest themselves after an incubation period 
of three to seven days. The symptoms following in¬ 
fection through the skin are characterized by headache, 
high fever, stiffness in the limbs, restlessness, and 
anxiety. Collapse frequently follows. The lymphatic 
glands are enlarged, particularly those in the inguinal 
region, which are called buboes. Infection by way of 
the respiratory tract begins abruptly with pneumonia. 
The mortality rate for this disease is very high,—80 
to 90 per cent. 
The bacilli of the plague are present in the swollen 
lymphatic glands, the sputum, urine, and intestinal 
discharges, and the infection may be spread directly 
from these sources. The chief way, however, in which 
the infection is spread is from the bites of the rat-flea, 
which transmits the disease from rat to rat and from 
rat to man. Unsanitary conditions have little to do 
with the occurrence of the plague, except that they 
favor infestation with rats. To prevent the disease 
from spreading, all patients must be quarantined, all 
discharges destroyed, and all articles that have come 
in contact with the patient disinfected. To prevent 
rats from, breeding, all stables and outhouses should be 
cleaned up, and all possible sources of food-supply cut 
off. Dwelling-houses should be made rat-proof as far 
as possible. The importation of the disease into ports 
not infected should be guarded against by fumigating 
ships from infected countries and the isolation of sus¬ 
pected cases during the period of incubation. 
The way 
the disease 
is spread 
Ways of 
prevention 
