BLOOD SERUM MEDIA 



41 



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 precautions, then 

 sterilisation of the serum 

 is unnecessary. To this 

 end the mouth of the 

 cylinder used for collect- 

 ing the blood, instead of 

 being plugged with wool, 

 has an indiarubber bung 

 inserted in it through 

 which two bent tubes 

 pass. The outer end of 

 one of these is of con- 

 venient length, and be- 

 fore 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 

 indiarubber 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 

 growth of the b. diphtherias, and may be used for other organisms. 

 It has the following composition : Three parts of calf's or lamb's 



FIG. 8. Blood serum inspissator. 



