52 METHODS OF CULTIVATION OF BACTERIA. 



placed, and the temperature being raised to 65 C., the 

 contents solidify in a sloped position in the interior. It is 

 well not only to have the jacket filled with water, but also 

 to put some water in the trough in which the tubes lie, 

 and also to have a thermometer in the water. This pre- 

 vents cooling of the tubes when the lid is raised to see 

 if the process is complete. As is evident, the preparation 

 of this medium is tedious, but its use is necessary for the 

 observation of particular characteristics in several patho- 

 genic 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 precautions, then 

 sterilisation of the serum is unnecessary. To this end the 

 mouth of the cylinder used for collecting 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 convenient 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. The serum obtained under such circumstances 

 must be incubated before use, to make sure that it is sterile. 



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

 the growth of the B. diphtheriae and may be used for 

 other organisms. It has the following composition. Three 

 parts of calfs or lamb's blood serum are mixed with one 

 part ordinary neutral peptone bouillon made from veal 

 with i per cent of grape sugar added to it. Though 

 this is the original formula it can be made from ox or 

 sheep serum and beef bouillon without its qualities being 

 markedly impaired. Sterilise by method B (4) as above. 



