This provides for the reduction as far as possible of contamination during the milking process itself.
If the contamination exceed a certain limit, the scrapings remain quite dead.
The unavoidable contamination with muddy particles of vat-waste is removed by allowing the vatliquor to rest for some hours in a separate tank and settling out the mud.
The tension for clean water thus found is considerably lower than that (81) adopted by Quincke, but it seems to be entitled to confidence, and at any rate the deficiency is not due to contamination of the surface.
Contamination isn't the only problem with the pet foods on the market today.