As if for now, you need to find the "correct" knife. Either the stone knife, kitchen knife, scalpel or survival knife (I think).

I'm currently working on a huge patch where you can even use bread knives etc, and modded knives from some mods I use. I will also try to compile a nice guide in the discussions, stating all items you can use for extracting zombie cells, probability calculators and so on, preparing you for the correct usage of the mod.

PS. There will be new items added to add deeper layers for your first aid skill development and risque control during this epidemic.

how do i godamningly extract zombie cells