far more profitable to put some of this time on the technical manipu¬ 
lation of the feces before making the slide to be examined, 
A Simple Technic 
The technical manipulation necessary to prepare more satisfac¬ 
tory slides for examining is designed to concentrate the parasite eggs 
originally scattered throughout the feces by removing that part of 
the feces which can readily be separated on the basis of differences 
in size, specific gravity, solubility, etc., in other words on the basis of 
physical and chemical differences. A simple technic that will give 
a high degree of concentration is as follows: Feces are broken up, 
screened through a set of screens placed in a rack with the coarse 
screens at the top and the finer ones at the bottom, the material 
passing through all the screens being caught in a suitable tray or dish; 
after standing a minute or so, the top half of this material is decanted 
and replaced by clean water; this process is repeated every minute 
until the soluble coloring matter and floating floeculent matter is 
poured away and the water stands clear on the sediment at the bot¬ 
tom; the water is then decanted until only a little is left on the 
sediment and this is shaken up and poured into a centrifuge tube 
till the tube is full; the tube is then set in a rack until ready to be 
examined. 
In the course of this manipulation, all fecal matter too coarse to 
pass through a screen of 100 apertures to the inch, which will allow the 
passage of the largest parasite eggs one need consider in work of this 
sort, has been eliminated by the screens; the soluble coloring matter 
and floating floeculent material which would obscure the view of the 
eggs on the slide have been eliminated by washing and sedimenting; 
what is left consists of parasite eggs and other material of approxi¬ 
mately the same size as the eggs or smaller, and material approxi¬ 
mately as heavy or heavier. 
When there is a bottom sediment evidently composed of sand in 
the tray or dish used to catch the feces passing through the screen, 
this should be allowed to stay in the dish and not rinsed into the 
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