The release by enforced activity of the cardiac accelerator from the corpus cardiacum of Periplaneta americana

Abstract

The potency of breis of the corpus cardiacum, as measured by their ability to increase the rate of beating of the isolated heart of Periplaneta, declines steadily with length of stimulation by tumbling in glass jars. Tumbling also brings about the appearance in the haemolymph of a potent stimulator of the cockroach heart; this factor is absent from tumbled decapitated cockroaches and from tumbled cockroaches lacking their corpora cardiaca. Tumbled cockroaches exhibit a lower proportion of argentaffin cells among their pericardial cells than normal cockroaches. The cardiac stimulator is shown to be confined to the intrinsic secretory portion of the corpus cardiacum. These findings are related to other substances which appear in stimulated cockroaches.