In rats fasted after the removal of about seven-tenths of the liver the remaining fragment undergoes ordinarily a marked simple hypertrophy and attains the weight reached through a process of simple atrophy by the entire liver of fasting controls. Under circumstances of exceptionally severe inanition, the hypertrophy may not occur, the fragment remaining unchanged or even undergoing a slight atrophy. But since in comparable controls the hepatic atrophy is extreme, the duplication in the liver weights still manifests itself.
It is difficult to avoid the conclusion that the liver changes which take place in fasting animal are essentially conditioned on functional demands made upon the organ. Yet great as is the hepatic atrophy then occurring, this does not necessarily mean that these demands are much lessened during inanition. For a comparison of the liver weight with that of the soft body (net body weight less the weight of the ligamentous skeleton) brings out the fact that the organ is, relatively speaking, three-fourths as large at extreme inanition as in the well nourished individual. Of the missing fourth a part may be foodstuffs on temporary deposit. And the rest is perhaps to be accounted for by the existence of special conditions during inanition which favor the vicarious assumption of a part of the usual liver work by the other tissues.
While the findings show that the liver size is essentially dependent on functional demands, they do not enable one to say whether the special demands in question come normally to the organ by way of the portal stream.