The McMaster
technique uses a counting chamber which enables a known volume
of faecal suspension (2 x 0.15 ml) to be examined microscopically.
Thus, if a known weight of faeces and a known volume of flotation
fluid are used to prepare the suspension, then the number of eggs
per gram of faeces (e.p.g.) can be calculated.
The quantities are chosen so that the faecal eggcount can be easily
derived by multiplying the number of eggs under the marked areas
by a simple conversion factor.
The McMaster chamber has two compartments, each with a grid etched
onto the upper surface. When filled with a suspension of faeces
in flotation fluid, much of the debris will sink while eggs float
to the surface, where they can easily be seen and those under the
grid counted.
