This midichloridian idea is quite interesting...
If something can be lost, it can be gained aswell!
So if we suppose that all people have some midichlorodians in their blood, the jedi should filter it from the blood people donate. And then give it to padawans. And if midichloridians are "animals", then their numbers would eventually grow larger and larger.
2 midis -> 4 midis -> 8 midis -> 16 midis ->32 midis ->64 midis ->128 midis ->256 midis -> 512 midis.... and the list goes on.
Im sure that the force sensitivity is more related to the chemical structure of subjects blood. Certain types of blood have inherently more nutrients for midichloridians.
lol . Too scientific.
But they needed a way to measure force.