40 METHODS OF CULTIVATION OF BACTERIA 



use is necessary for the observation of particular characteristics 

 in several pathogenic bacteria, notably the tubercle bacillus. 

 Pleuritic and other effusions may be prepared in the same way, 

 and used as media, but care must be taken in their use, as we 

 have no right to say that pathological effusions have the same 



chemical composition as 

 normal serum. 



If blood be collected 

 with strict aseptic precau- 

 tions, then sterilisation of 

 the serum is unnecessary. 

 To this end the mouth of 

 the cylinder used for col- 

 lecting the blood, instead 

 of being plugged with wool, 

 has an india-rubber bung 

 inserted in it through 

 which two bent glass tubes 

 pass. The outer end of 

 one of these is of conveni- 

 ent length, and, before 

 sterilisation, a large cap of 

 cotton wool is tied over it ; 

 the other tube is plugged 

 with a piece of cotton wool. 

 In the slaughter-house the 

 cap is removed and the 

 tube is inserted into the 

 blood-vessel as a cannula. 

 The cylinder is thus easily 

 filled. Another method is 

 to conduct the blood to 

 the cylinder by means of 

 a sterilised cannula and 

 india-rubber tube, the 

 former being inserted in 

 the blood-vessel. In every case the serum must be incubated 

 before use, to make sure that it is sterile. 



Coagulated Blood Serum. If fresh serum be placed in 

 sterile tubes and be steamed in the sloped position for an hour 

 it coagulates, and there is thus obtained a solid medium very 

 useful for the growth of the diphtheria bacillus for diagnostic 

 purposes. 



Loffler's Blood Serum. This is the best medium for the 



FIG. 8. Blood serum inspissator. 



