Regeneration of the liver following partial hepatectomy has been studied in three groups of rats: young, adult, and old. The livers of the young rats exhibited smaller cells and a much higher degree of binuclearity. Those of the old rats were often indistinguishable from the adults, although they did frequently show certain abnormalities which were rare in the younger animals. During regeneration, the changes in the histological picture were similar in all three groups.

In young rats, regeneration was superimposed upon the normal process of body growth; hence, this group was not strictly comparable to the others. When corrections were made for the various factors associated with growth, however, it seemed that these rats still greatly exceeded the others, in ability both to restore liver mass and to form new cells.

The old rats equaled the adults in ability to regenerate liver mass but lagged behind somewhat in cell production.


This work was supported by a grant from the American Cancer Society. This is publication No. 699 of the Harvard Cancer Commission.

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