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 

 iufected 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. 



