Other views about the hepatotrophic concept.

: In this paper two main questions are approached. The first relates to the aspects of the proliferative response which are influenced by alleged hepatotrophic substances and experiments will be recounted which were designed to test whether hepatocyte enlargement and division are separable. Both short-term and long-term data suggest the need to consider that these two reactions may be controlled by different factors. The second question is concerned with the indentification of hepatotrophic substances and the circumstances in which these are found to be effective. Experiments have been carried out which attempt to assess the extent to which normal liver cells are affected by specific hepatotrophic substances in vivo. The findings do not completely support the hypothesis that the integrity of the liver cell is dependent on a single identifiable hepatotrophic substance.