Methods. The methods adopted in the investigation of the movements of the rabbit's small intestine were very similar to those adopted in our previous research. We found however that the wall of the rabbit's intestine was at the same time too delicate and too excitable to give any reliable results with the enterograph, so that all our tracings were obtained by the insertion of a rubber balloon in the lumen of the gut. This was distended with air under the pressure of about one inch of water, and connected with a piston recorder. The much greater excitability of the rabbit's intestine as compared with that of the dog, and the mode of its contraction may render the balloon method unreliable unless controlled by ocular inspection. At the same time the spontaneous variations in the activity of the gut renders the method of simple inspectionin many cases misleading, although observations of this character have the advantage that they can be carried out without the introduction of an abnormalirritant like the balloon into the lumen of the intestine.