How can you distinguish between dog hair and cat hair at microscopic level?

Cat hairs are usually thinner, covered with distinct scales, sometimes spiny/pointed (visible at 40X)--I think that's why cat hair sticks to everything! The medulla, or central "core" has a ladder-like appearance.

Dog hairs are usually somewhat thicker, although it varies. Scales are not as obvious. The medulla doesn't look like a ladder, but it can appear somewhat bubbly; sometimes it's very wide. There may be obvious pigment granules in the cortex, or outer layer. The root, if you have one, is spade-shaped.