Page:Blood examination.djvu/16

4 Differential count—

It should be remembered that in children the polymorphonuclears vary from 28 to 40 per cent., and the small lymphocytes, being increased, vary between 40 and 60 per cent.

The value of examining fresh blood films is very evident when we have to deal with malaria, trypanosomiasis, filariasis or spirilla.

In malaria, not only do the movements of the parasites in the corpuscles once seen render a mistake in diagnosis almost impossible, but according to the activity of the movement we are also helped to judge as to whether the infection is benign tertian, quartan, or sub-tertian; the pigment also shows up more distinctly in fresh films, and gives us further help in differentiation.

Trypanosomes, spirilla and filaria, on account of the active movement they cause amongst the corpuscles, are usually fairly easily found in fresh films.

Filaria nocturna embryos occur in the peripheral blood only at night, or by day in