I randomly measured MDL-IPL distances in approximately 90 myelinated axons from the mouse optic nerve, with axon diameters ranging from 0.3 to 1.2 μm. For each axon, I selected 3 wraps in the inner region, 3 in the mid-region, and 3 in the outer region of the myelin sheath.

In nearly all cases, the outer wraps showed greater MDL-IPL distances than the mid and inner ones, while there was no clear difference between mid and inner layers.

I’m wondering if this observation reflects a biological property of myelin structure. Can this be generalized to larger axons — for example, those with diameters around 3 μm