DIPHTHERIA. 4c 
7 
cork and wire of the swab tube are now withdrawn and 
the cotton-wool plug is inserted into the culture tube 
and passed onwards until it reaches the sloped surface 
of the medium. It is then rubbed gently on the latter 
and twisted round and round so that every part of the 
swab may come into contact with the medium. If there 
is a piece of membrane special care should be taken to 
see that it is rubbed on the surface, for it is here that 
we are most likely to find the bacilli. The swab is now 
withdrawn and replaced in the tube, and the cotton- 
wool plug of the culture tube singed and replaced. 
The tube thus inoculated must now be incubated for 
about 18 hours at a temperature not exceeding 37° C., 
and is then ready for examination. 
Hewlett has suggested a useful method which may 
be carried out without any special apparatus, the white 
of a hard-boiled egg being used as the culture medium. 
Take a fresh egg and boil it for ten minutes or more 
and allow it to cool. Now take a narrow-mouthed 
wineglass (or a wide-mouthed bottle, which is better) 
and rinse it out with perchloride of mercury lotion. 
Sterilise a knife by passing it slowly through the flame, 
and cut off the top of the egg, care being taken not to 
cut into the yolk. Invert the egg into the wineglass 
(which must be narrow enough to prevent the egg from 
dropping down into it) taking care that none of the 
lotion touches the cut surface. This is the culture 
medium, and it is sterilised ready for inoculation. At 
a pinch it may be incubated in a warm corner near the 
fire, near the hot water cistern, or other warm place. 
