92 
BACTERIOLOGY. 
stained, and examined under the microscope. If 
diphtheria bacilli are present they can be readily iden¬ 
tified by their appearance. (See Schick test.) 
the r d a isea°se The disease is spread to others chiefly by means 
of the bacilli thrown from the nose or mouth by cough¬ 
ing and sneezing. The sputum contains the bacilli in 
large number. Indirectly the disease is spread from 
the sputum by means of drinking-cups, handkerchiefs, 
door-knobs, and among children from pencils, chewing 
gum, toys, and other things that are handled and 
passed about. Cats, rats, and mice may carry the in¬ 
fection, and flies may deposit it on food and milk. In¬ 
fected milk has been the cause of a number of epi¬ 
demics. 
The most important and first precaution to be 
taken in limiting the spread of diphtheria is isolation. 
This means the complete isolation of the sick person. 
The length of the isolation cannot be determined by 
the condition of the patient or by the appearance of the 
throat, because it is possible and frequently is so, that 
although the patient is apparently well and the throat 
clear, the bacilli of diphtheria are still there. In order 
to tell when the bacilli have disappeared a wiping of 
the throat is made just as described in making the 
diagnosis, incubated, and examined. 
Two such cultures free from diphtheria bacilli are 
considered sufficient evidence that the patient is no 
longer able to transmit the disease to others. In some 
cases virulent bacilli persist in the throat for months. 
Even in healthy persons, particularly attendant upon 
