Abstract
Electron-micromeasuring studies have been made on the hepatic cell mitochondria of the long lived parabiotic unions between old and young rats. The mitochondria of the younger partners were significantly larger in size and those of the older partners were significantly larger in number and smaller in size compared with those of young and old control rats respectively. The mitochondrial cristae seemed to become more compactly arranged in the younger partners and more sparsely in the older ones. Some discussions have been made on the influence of the parabiosis with different aged rats upon age change of the mitochaondria and of their function.
