It is well known that the tonus of the stomach depends, in part, on impulses from the vagi, and that the stimulation of the peripheral end of the vagi induces strong contractions in the stomach, whether empty or filled with food. It is also known that the stomach is capable of carrying out the movements of digestion to a fair degree of efficiency after section of both the vagi and the splanchnic nerves. In other words, the neuromuscular apparatus of the stomach seems to be primarily automatic as regards the genesis of the movements of the digestion.

The experiment of sectioning the vagi does not prove this point, however. The experiment does prove the plasticity of the gastric motor mechanism. One would expect that the extrinsic gastric nerves bear the same relation to the movements of the filled and of the empty stomach. This phase of the problem cannot be studied in man. If it should develop that the periodic hunger contractions of the empty stomach are caused by periodic discharges through the vagi, the ultimate question of the cause of hunger would again become a problem of physiology of the central nervous system.