The factors concerned in the contraction and evacuation of the gallbladder have been greatly clarified by Ivy and his collaborators,1 who have shown that the introduction of acid or of digested fat into the duodenum liberates a hormone, named by them "cholecystokinin," which causes an active contraction of the viscus. Their work indicates that this liberation of cholecystokinin is one of the principal mechanisms by which evacuation of the gallbladder is effected. In view of their reports, an evaluation of other possible mechanisms is of importance.
REFLEX AND DIRECT STIMULATION OF THE EXTRINSIC NERVES
The literature on the extrinsic nerves of the gallbladder was reviewed in 1924 by Mann,2 who was led to conclude that the vagus is mainly motor and the splanchnic mainly inhibitory. Experimental work up to this time had been largely concerned with stimulation of the nerves under anesthesia and by means of drugs, but