136 GENERAL BACTERIOLOGICAL DIAGNOSIS 



(1) that every precaution must be adopted to prevent the 

 material from being contaminated with extraneous organisms; 



(2) that nothing be done which may kill any organisms which 

 may be proper to the inquiry ; and (3) that the bacteriologist 

 obtain the material as soon as possible after it has been removed 

 from its natural surroundings. 



The sources of materials to be examined, even in patho- 

 logical bacteriology alone, are, of course, so varied that we can 

 but mention a few examples. It is, for instance, often necessary 

 to examine the contents of an abscess. Here the skin must be 

 carefully purified by the usual surgical methods the knife used 

 for the incision is preferably to be sterilised by boiling ; the first 

 part of the pus which escapes is allowed to flow away (as it might 

 be spoilt by containing some of the antiseptics used in the 

 purification), and a little of what subsequently escapes allowed 

 to flow into a sterile test-tube. If test-tubes sterilised in a 

 laboratory are not at hand, an ordinary test- 

 tube may be quarter-filled with water and 

 vigorously boiled over a spirit-lamp. The tube 

 is then emptied and plugged with a plug of 

 cotton wool, the outside of which has been 

 singed in a flame. Small stoppered bottles 

 may be sterilised and used in the same way. 

 A discharge to be examined may be so small 

 in quantity as to make the procedure described 

 impracticable. It may be caught on a piece 

 of sterile plain gauze, or of plain absorbent 

 wool, which is then placed in a sterile vessel. 

 Wool or gauze used for this purpose, or for 

 swabbing out, say the throat, to obtain shreds 

 of suspicious matter, must have no antiseptic 

 impregnated in it, as the latter may kill the 

 bacteria present and make the obtaining of 

 cultures impossible. 



Fluids from the body cavities, urine, etc., 



FIG. 46. Test-tube mav j^ secure d w ith sterile pipettes. To make 



and pipette ar- J , . _ . . r f ,. .,, 



ranged for obtain- one o* these, take 9 inches of ordinary quill 



ing fluids contain- glass-tubing, draw out one end to a capillary 



diameter, and place a little plug of cotton wool 



in the other end. Insert this tube through 



the cotton plug of an ordinary test-tube, and sterilise by heat. 



To use it, remove test-tube plug with the quill tube in its centre, 



suck up some of the fluid into the latter, and replace in its 



former position in the test-tube (Fig. 46). Another method 



