The Breakdown of the Thoracic Gland in the Adult Insect, Rhodnius Prolixus

The thoracic gland in Rhodnius breaks down and disappears within 48 hr. after the moult to the adult stage. Two factors are involved: (i) The gland suffers some change as the result of going through a moulting stage in the absence of the juvenile hormone. (ii) It must then be exposed to some humoral action at the time of the adult moult. The source and nature of the stimulus which operates at the time of the final ecdysis are not known. But when the gland has been exposed to these two changes it will rapidly break down even in an environment containing the juvenile hormone.

The function of sympathetic nerves in relation to skeletal muscle—evidence for humoral action

In a previous paper (Corkill and Tiges, 1933) evidence was given that the increase in strength of contraction which occurs in fatiguing skeletal muscle when its sympathetic nerves are stimulated (Orbeli’s effect) exhibits certain features which point to a humoral mode of origin. This humoral action is suggested (i) by the presence of the effect long after sympathetic stimulation has ceased, (ii) by an increase in latent period of onset of successive rsponses when they progressively weaken, (iii) by the fact that the effect may be reproduced by appropriate treatment with adrenaline. A purely vascular origin of the effect having been excluded, the humoral interpretation would seem to offer a means of recording the occurrence of the phenomenon with the apparent absence of a direct sympathetic supply to the muscle tissue; for the only sympathetic nerves in muscle whose existence is beyond dispute are those its blood vessels.