Figure 5. Electron micrograph of tree shrew and human cornea fixed in 2.5% glutaraldehhyde containing cuprolinic blue and embedded in spurr resin. A: Electron micrograph of proteoglycans of tree shrew stroma. B: Digital image obtained after processing image shown in A, showing variable area distribution of PGs. C: Electron micrograph of proteoglycans of human stroma. D: Digital image obtained after processing image shown in C, showing variable area distribution of PGs. PG=Proteoglycan; Proteoglycans color coding: Red=50–350 nm², Green=350–650 nm², Blue=650–950 nm², Yellow=950–1,250 nm², Aqua=1,250–1,550 nm², Pink=1,550–1,850 nm², and Brown=1,850–2,150 nm².