Abstract
The extent of the peripheral parasitaemia of the Trypanosoma rotatorium complex in bullfrogs (Rana catesbeiana Shaw) is subject to fluctuations depending on the metabolic state of the host. Electrical stimulation causes a significant increase in the peripheral haemoflagellate levels. Moreover, injections of adrenalin chloride solution result in a similar response, while injections of acetylcholine and hypertensin do not. Adrenalin may act directly on the trypanosomes or indirectly via the host through such phenomena as elevated glucose levels. Blood pressure does not appear to be a factor.