62 PRACTICAL BACTERIOLOGY. 



For the stroke cultures we use the test-tubes, in 

 which the gelatine or agar-agar has solidified ob- 

 liquely. Some of the bacterium colony is taken up 

 with the sterilised platinum wire, and the nutrient 

 medium is inoculated with it. The whole process of 

 this inoculation is as follows : after having thoroughly 

 heated the platinum wire, and having allowed it to 

 cool for about two minutes without laying it down 

 or letting it touch anything, the operator takes up 

 with its point a small portion of the colony to be 

 inoculated, seizes with the left hand the test-tube 

 which is in readiness, containing the oblique nutrient 

 substance, and draws out the plug of wadding with 

 the third and fourth fingers of the right hand, laying 

 the backs of the fingers upon it, so that the part of 

 the plug which goes into the tube, and which it is 

 essential to keep sterilised, should touch neither the 

 hand nor any other object ; the platinum wire is then 

 passed very carefully into the test-tube, so as not to 

 touch the sides with it, and is drawn gently across the 

 centre of the nutrient medium, care being taken not 

 to injure the surface. The platinum wire is then with- 

 drawn, and the cotton-wool plug replaced, the stroke 

 inoculation being completed. It is also necessary in 

 this case to work as quickly as possible, lest germs 

 from the air should get in. During the operation the 

 test-tube is held horizontally, or if anything with the 

 bottom a little higher than tbe mouth. 



