This study of hunger, reported by Washburn and myself in 1912, has since been taken up by Carlson of Chicago, and in observations on a man with a permanent gastric fistula, as well as on himself and his collaborators, he has fully confirmed our evidence as to the relation between contractions of the alimentary canal and the hunger sensation. In a series of nearly a score of interesting papers, Carlson and his students[208] have greatly amplified our knowledge of the physiology of the “empty” stomach. Not only are there the contractions observed by Washburn and myself, but at times these may fuse into a continuous cramp of the gastric muscle. The characteristic contractions, furthermore, continue after the vagus nerve supply to the stomach has been destroyed, and, therefore, are not dependent on the reception of impulses by way of the cranial autonomic fibres. Recently Luckhardt and Carlson have brought forward evidence that the blood of a fasting animal if injected into the vein of a normal animal is capable of inducing in the latter the condition of cramp or tetanus in the gastric muscle mentioned above--an effect which does not occur when the blood of a well-fed animal is injected. It seems _possible_ that a substance exists in the blood which acts to excite the gastric hunger mechanism. But this point will require further investigation. With these demonstrations that contractions are the immediate cause of hunger, most of the difficulties confronting other explanations are readily obviated. Thus the sudden onset of hunger and its peculiar periodicity--phenomena which no other explanation of hunger can account for--are at once explained. In fever, when bodily material is being most rapidly used, hunger is absent. Its absence is understood from an observation made by F. T. Murphy and myself,[209] that infection, with systemic involvement, is accompanied by a total cessation of all movements of the alimentary canal. Boldireff observed that when his dogs were fatigued the rhythmic contractions failed to appear. Being “too tired to eat” is thereby given a rational explanation. A pathological form of the sensation--the inordinate hunger (bulimia) of certain neurotics--is in accordance with the well-known disturbances of the tonic innervation of the alimentary canal in such individuals.