Transmission electron microscope of a large dividing mitochondrion in a liver cell of a mouse recovering cuprizone intoxication. Treatment with this drug results in the formation of a giant hepatic mitochondria. Withdrawal of the drug induces the giant organelles to divide by medial attenuation. The mitochondria become very slender in their mid-portions, and eventually pinch off to form two daughter cell organelles. Magnification 68,000 @ 8x10 inches.