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Blood vessels from skeletal muscle, coloured scanning electron micrograph (SEM). Skeletal, or voluntary, muscle is that under the conscious control of the brain. This is a cast: the vessels were filled with a resin, which then set. The surrounding tissues were then eaten away chemically, leaving the cast of the vessels. Magnification: x430 when printed 10cm high. (KEYSTONE/SCIENCE PHOTO LIBRARY/SUSUMU NISHINAGA)