SPECIAL BACTERIOLOGY 
175 
not that they were born of tuberculous parents, but be¬ 
cause they live with them. Prevention means isolation 
of the patient, disinfection of sputum and other excreta 
and linen, etc., fumigation of the room, etc. See special 
chapter on Disinfection and Fumigation. 
VI. Mechanism of Infection and Immunity 
The tubercle bacillus produces an endotoxin (tuber¬ 
culin). Tuberculin, prepared in several ways, is used 
for diagnosis of the infection; no cattle is to be killed 
for food unless it has been tested with tuberculin, as also 
should all cows producing milk for sale. In human be¬ 
ings the tuberculin test is applied into or under the skin, 
and in infected individuals. Such injection causes a 
marked reaction at the site of injection. This test is 
called von Pirquet’s test. The antibodies produced by 
infected animals and human beings are essentially bac- 
teriolysins. 
VII. Bacteriologic Diagnosis 
Bacteriologic diagnosis rests on finding the bacilli 
stained by the special method (described in chapter on 
Staining). If this fails, sputum or urine may be in¬ 
jected intraperitoneally into a guinea pig and if the 
animal does not die in three or four weeks, it is killed, and 
evidences of tuberculosis are looked for at the site of 
injection, in the lungs, liver and spleen. Tuberculin test 
and, recently, complement-fixation test (similar to Was- 
sermann test for syphilis) are of great value. 
VIII. Immune Treatment. 
No such treatment is very successful, although vari¬ 
ous authors have claimed good results obtained in some 
cases treated with small doses of tuberculin. 
