TISSUE

ABORTION associated with mycotic placentitis is well known in cattle and causes considerable economic loss in Britain (Austwick and Venn, 1961; Hugh-Jones and Austwick, 1967). Occasionally foetal infection occurs but the dam usually shows no ill effects, spontaneously recovers after aborting, and may subsequently conceive normally (Ainsworth and Austwick, 1959). Al-though numerous fungi have been implicated in the disease (Ainsworth and Austwick, 1959; Campbell, 1969) Aspergillus fumigatus is the major causal organism, accounting for over 60 % of cases in Britain and the USA (Austwick and Venn, 1961; Hillman, 1969). Intravenous inoculation of the conidia of A. fumigatus into sheep and cattle led to abortion with striking localisation of hyphal growth in the placentae (Cysewski and Pier, 1968; Hillman and McEntee, 1969). Extra-placental lesions may develop after intravenous inoculation but these either remain small or rapidly disappear whereas infection persists and spreads throughout the placentae of both the cow (Hill et al., 1971) and sheep (Pier, Cysewski an