In the past there used to be engines without oil filters or with oil filters in the bypass flow where the oil stream was divided. These, however, also had shorter change intervals than today. A modern engine without oil-filtering is unthinkable nowadays. In the picture below is an example of a species although still alive, it is slowly threatened with extinction.
These filters have to be exchanged complete with the casing and must be disposed of. They are screwed together at the upper end and are sealed. They filter metal abrasion, dust and combustion residue up to a few thousandths of a millimetre in size using folded paper. Modern filters do this no differently, however, the casing is reusable, only the paper insert is changed, the oil remains in the filter module. 06/08