Quill of North American porcupine (Erethizon dorsatum) by SEM. The quill was obtained from a dead animal. About 0.6 cm from the tip, the quill tapers to a fine point, closely covered by several dozen small black barbs. These barbs feel only slightly rough to the touch, but when they are moist (as when embedded in flesh) they swell, working the quill farther in. The quills have black tips and yellow or white shafts. Under a microscope, the tips appear as if they have scales or shingles, not barbs, that point backward. Once embedded in the flesh, they may be difficult to remove, especially the tiny ones that break before they are extracted. Each North American porcupine has over 30,000 quills. It lashes its tail threateningly when disturbed, possibly detaching loose quills, which fly through the air as though they were thrown. Enhanced SEM. Image width 1.7 mm. Magnification: 59x if the image is printed 10 cm wide. Bar: 200 micrometers.