Abstract
SUMMARY: Virulent and avirulent strains of Leptospira icterohaemorrhagiae did not grow from inocula of fewer than 107 organisms/ml, in Korthof medium, but did grow when FeCl3 or preparations containing iron porphyrins were added. With added FeCl3 or haematin growth was somewhat slower than when the iron porphyrin-containing preparations were added.