Studies on Internal Secretion Iii.—the Action of Pituitary Extract and Adrenaline on Contractile Tissues of Certain Invertebrata.*

T H E present investigation was undertaken by the senior author in the first place to shed further light on two questions which emerged in the course of investigations on the role of the pituitary in the regulation of colour response (Hogben and Winton, 1922-23, Hogben, 1923-24). These were: (a) how far the action of pituitary extract is a specific one for the uterus or extends to contractile tissues generally; (6) with what justification the action of adrenaline on an effector organ may, in the absence of direct evidence, be regarded as indicative of sympathetic innervation. Study of the action of vertebrate autocoids on the contractile tissues of Invertebrata was therefore undertaken ; and after preliminary experiments directed to select suitable materials it was decided to confine attention to the isolated heart of the crab (Maia squinado), the perfused heart of the scallop (Pecten maximus), the isolated crop of the sea-slug (Aplysia), and the isolated pharynx of the sea-mouse {Aphrodite). The first was suggested by Carlson's work (1905) on Limulus, the only arthropod in which an isolated heart