242 BACTERIOLOGY 



obtain the materials under aseptic precautions, care being 

 taken that no disinfectant fluids are mixed with them. 

 They should be subjected to study as soon as possible after 

 removal from the body. In the case of tissues that cannot 

 be examined on the spot, they should be placed in a sterile 

 Petri dish or in a stoppered, sterile, wide-mouthed bottle 

 and taken at once to the laboratory. The surface should 

 then be seared with a hot knife and an incision through the 

 seared area into the centre made with a knife that has been 

 sterilized and allowed to cool. From the depths of this 

 incision enough material may be obtained for microscopic 

 examination and for the preparation of cultures. Fluid 

 exudates that must be taken to the laboratory should be 

 collected in either a sterile test-tube, or, better, in a sterile 

 capillary tube that is subsequently sealed at both ends in 

 a gas-flame. When bacteriological examination of the 

 blood during life is required, it is customary to obtain the 

 necessary sample of blood by pricking the skin. It must 

 be remembered, in this connection, that the skin usually 

 contains a number of species of bacteria that are of no 

 pathological significance and have nothing to do with the 

 disease from which the individual may be suffering. It is 

 manifestly essential to exclude these. It is not possible to 

 exclude them certainly and completely under all circum- 

 stances, without a more or less elaborate procedure; but 

 an effort to do so should always be made. As a rule, the 

 greater number of them may be removed from the skin by 

 careful washing with warm water and soap and a sterile 

 brush, after which the skin should be rinsed with alcohol 

 and allowed to dry spontaneously. The drop of blood may 

 then be obtained from the skin thus cleaned by a prick 

 with a sharp, sterilized lancet. The presence in the cultures 



