Abstract
The stimulatory substance (SS) that is found in the cytosol of regenerating dog livers and which promoted regeneration when injected into the portal vein after Eck fistula did not cause glomerular proliferation when active cytosol was injected into the renal artery. The finding was compatible with but did not prove organ specificity of hepatic SS. The development of SS was completely prevented by extirpation of all nonhepatic splanchnic organs at the same time as partial hepatectomy. This finding indicated that SS in the cytosol donors was a feature rather than an initiator of regeneration, and one that depended upon the collaboration of extrahepatic (including splanchnic hepatotrophic) factors.