242 BACTERIOLOGY. 
From wounds, abscesses, cellulitis, etc., the substance 
for bacteriological examination can, as a rule, best be. 
obtained by means of small rods armed with a little 
absorbent cotton. A number of these can be carried 
in a test-tube. Both rods and tubes must be sterile. 
-The swab is inserted in the wound, then streaked 
gently over the oblique surface of the nutrient agar in 
one tube, over the blood-serum in another, and then 
inserted in the bouillon. Finally, either at the bed- 
side or in the laboratory, material is thinly streaked 
over the surface of nutrient agar contained in several 
Petri dishes. We inoculate several varieties of media, 
with the hope that one at least will prove a suitable 
soil for the growth of the organisms present. From 
surface infections of mucous membranes, as in the 
nose, throat, vagina, etc., the swab, again, is probably 
the most useful instrument for obtaining the mate- 
rial for examination. The greatest care, of course, 
must be used in all cases to remove the material for 
study. without contaminating it in any way by other 
material which does not belong to it. Thus, for in- 
stance, if we wish to obtain material from an abscess 
of the liver, where the organ lies in a peritoneal cavity 
infected with bacteria, here one must first absolutely 
sterilize the surface of the liver by pressing on it the 
blade of a hot iron spatula before cutting into the ab- 
scess, so that we may not attribute the infection which 
caused the abscess to the germs which we obtained from 
the infected surface of the liver. From such an organ 
as the uterus it is only with the greatest care that we 
can avoid outside contamination, and only an expert 
bacteriologist familiar with such material will be able 
to eliminate the vaginal from the uterine bacteria. 
