1085 
Microbiology. — ‘Penetration of methyleneblue into living cells 
after desiccation”. By Prof. Dr. M. W. Brverrinckx. 
(Communicated in the meeting of December 28, 1912). 
It is generally known that methyleneblue does not enter living 
yeastcells, when these are first soaked with water or swimming in 
a fermenting liquid, whilst it colours the dead cells intensely. It is 
even possible several days to cultivate yeast in wort, coloured dark 
blue with this pigment, without the cells being coloured in the least. 
On wortagar plates with methyleneblue, colourless colonies will 
develop. On these facts a method is based to ascertain in living yeast 
the number of dead cells, which gives very good results. 
Meanwhile there is an exception to the rule that the cells, colouring 
blue are dead, and this exception will be more closely considered here. 
At the examination of dried yeast, most cells of which take a 
dark blue colour with methyleneblue, whilst only a very small per- 
centage remain colourless, the fermenting power often proves so great, 
that no other explanation can be given, bat that the blue-colouring 
cells have for the greater part preserved that power. This is not 
unexpected, for it is well known that the alcoholic function is more 
permanent in dieing cells than the power of growth. Meanwhile, 
counting-experiments, whereby on one hand the number of cells colour- 
ing with methyleneblue was microscopically determined, on the other 
hand by plate culture, that of the cells growing out to colonies, showed 
that from certain dry yeast samples a much greater percentage of 
colonies developed, than the percentage of celis not colouring with 
methyleneblue. This fact was indeed unexpected and induced to a 
more minute observation. 
First of all it was proved that the number of cells, colouring in 
a dilute solution of methyleneblue, depends on the way in which 
the solution is brought into contact with the cells. If this is done 
by introducing dry yeast into the solution, all the cells colour dark- 
blue and cannot be distinguished from the dead ones. In plate cul- 
tures, however, a greater or smaller number of colonies may be 
obtained from these cells, although all seem perfectly alike in their 
dark blue colour, and should be considered as dead by anyone 
ignorant of their origin. In favourable circumstances the number 
of colonies mounts even to 100°/,, which is to say, that all the 
cells may colour blue and still grow out to colonies. 
This is in particular obvious when the cells are beforehand 
coloured with methyleneblue, and the coloured material is used for | 
