CULTIVATION ON PLATES AND IN TUBES. 53 



introduced with, a sterilised instrument into the gela- 

 tine and is then well mixed with it. This mixing is 

 most easily done by tipping the dish from side to side, 

 care being taken that the contents should not run 

 over the edge. When this has been successfully ac- 

 complished, a small quantity of the mixture is taken 

 out of the dish with a sterilised wire and is then well 

 mixed with the gelatine of another dish. Similarly, 

 some is taken out of the second dish and mixed with 

 the contents of a third. The instrument best adapted 

 for carrying the meat infusion and gelatine is a piece 

 of platinum wire, about 10 cm. long and "8 mm. thick, 

 one end of which, has been fused on to the end of a 

 glass rod, while the other has been twisted up into a 

 little oval loop, about 2 mm. in its greatest diameter. 

 This wire is specially well adapted for carrying over 

 liquids, as a sufficiently large drop is easily retained 

 in the loop, and in addition it can be quickly sterilised 

 by holding it in a gas or spirit flame. In laying the 

 wire down to cool, which takes about two minutes, 

 especial care must be taken to prevent its touching 

 anything, the glass rod alone being allowed to rest on 

 the table, whilst the wire stretches over the edge. The 

 beginner cannot be too strongly urged to take the 

 greatest care of all sterilised apparatus and instru- 

 ments, and always to bear in mind that the hands, 

 and indeed the whole body, are covered with bacteria, 

 and- that if the platinum wire is touched or put to the 



