CHAPTER VII. 

 COLLECTION OF MATERIAL. 



All material used for bacteriological examination should 

 be fresh, for the reason that changes in the number as well as 

 the kinds of bacteria take place quickly in such material as 

 furnish a suitable soil for the development of bacteria under 

 ordinary circumstances. Samples of water or milk should be 

 examined as soon after drawing as possible; but when this is 

 impossible, as in the case where they are transmitted from a 

 distance, they should be collected in sterilized tubes or bottles, 

 which should be kept on ice but not frozen. Specimens of 

 sputum should be collected in clean bottles tightly corked. 

 The early morning sputum is to be preferred for examination. 

 The patient should be directed to rinse out the mouth carefully, 

 and cough up material from the lungs, not merely to clear out 

 the throat as is sometimes done. It should be examined as 

 soon as possible. Although decomposition appears not to 

 interfere with the staining properties of the tubercle bacilli, 

 the sputum should be fresh in order that the other bacteria 

 contained in it may be studied. Therefore, it should be free 

 from contamination with putrefactive germs. Valuable infor- 

 mation can also be obtained by examination of sputum in 

 a fresh condition before staining (see also page 34). 



Samples of urine keep better after the addition of a few 

 crystals of thymol, which retards the, fermentative process, so 

 that the sedimentation of the bacteria and of other solid mat- 

 ter in conical vessels is facilitated, although that purpose 

 can be accomplished at once by the centrifuge. Thymol will 

 also be a useful addition, as far as a bacteriological examina- 



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