On The Physiology and Pharmacology of the Earthworm Gut

Abstract

1. The gut of Lumbricus terrestris and Allolobophora longa was studied. 2. The normal movements of the different parts of the gut, isolated and suspended in Ringer's fluid, are described. 3. Acetylcholine excites all parts of the gut. The "crop and gizzard" preparation is very sensitive to acetylcholine and shows a graded series of responses over a wide range of concentrations. It may therefore prove to be useful in the assay of acetylcholine. 4. The action of acetylcholine on the crop and gizzard is only slightly increased by eserine or prostigmine. The potentiation is especially noticeable in the presence of other drugs (adrenaline, histamine) which interfere with the acetylcholine action. 5. The action of acetylcholine on the crop and gizzard is abolished by atropine. 6. Adrenaline excites the buccal cavity, pharynx and oesophagus in all concentrations. On the crop, gizzard and intestine it has two actions, inhibition above and excitation below a certain threshold concentration, whose magnitude varies somewhat from worm to worm. 7. The action of adrenaline is slightly increased by ephedrine, and abolished by ergotoxine. 8. The actions of choline, histamine, potassium and calcium on the crop and gizzard are described. 9. The crop and gizzard receive two sets of nerves: (a) Exciting nerves, coming along the gut wall from the circumpharyngeal nerve ring; action abolished by atropine; probably cholinergic. (b) Inhibiting nerves, coming along the septa from the ventral nerve cord; action abolished by ergotoxine; probably adrenergic.