IMMUNITY. 105 
The Use of Local Treatment in Inhibiting Bacterial In- 
vasion. The total extirpation of the infected area by 
surgical means, if thoroughly carried out, removes the 
disease entirely; but, unfortunately, this procedure is 
rarely possible. When incomplete it is frequently 
helpful; but it may be harmful, for by creating and 
exposing fresh wounded surfaces to infection it may 
lead to the further development of the disease. Again, 
it may be useless, for by removing only a portion of 
the bacteria it may leave those which have already 
reached the deeper tissues or blood to go on devel- 
oping. In some cases, like anthrax and infection 
from bites of rabid animals, total removal of the 
virus is possible, either by the knife or thorough cauter- 
ization, and will prevent a general infection. So also 
in tetanus, the invasion being limited, surgical inter- 
ference may be of great use by removing not only the 
bacilli themselves but also that portion of their poison 
which has not as yet been absorbed from the tissues. 
The beneficial effects of opening an abscess, incising a 
cellulitis, or cleansing and drainage of the uterine 
cavity are well known. The retention of the poisonous 
products of the bacteria and altered tissue substance 
leads to their absorption, and thus lowers the tone of 
the neighboring, and to a less extent of the general, 
tissues in consequence of the poisoning. This enables 
the bacteria to penetrate into tissues which would other- 
wise resist them. The mechanical effect of pressure on 
the walls of an abscess by its contents also aids the bac- 
terial progress. Local bleeding and the application of 
cold probably act by lessening tension. The application 
of warmth hastens absorption, and so, when the infec- 
tion is one which tends to localize, it acts favorably by 
