Discussion and Summary Intravenous infection of rabbits with neurotropic herpes simplex virus is only occasionally possible according to Le Févre de Arric and Millet1 Doerr and Vöctung,2 and Van Rooyen and Rhodes.3 This fact is borne out by our control series. The fact that all experimental animals in the series here reported were infected clearly reveals the potentiating effect of histamine shock on susceptibility to the virus. It would seem, from the first animal reported, that the effect is related to a common denominator of histamine and true anaphylactic shock.