. Many apparently normal persons experience in hunger, besides the gnawing pressure-pain sensation in the stomach, a feeling of weakness, "emptiness," headache, and sometimes even nausea. A certain degree of increased excitability of the central nervous system, as shown by restlessness, irritability, diminished concentration and attention, and some salivation are always present and must be looked upon as a necessary effect of hunger rather than accessory elements.
We call these states or symptoms accessory hunger phenomena, because they are not always present in hunger, and because their relative preponderance depends on the length of starvation and on some individual peculiarity in the person. It must be admitted, however, that in some individuals these accessory hunger phenomena appear to overshadow, if not entirely to suppress, the pressure-pain sensations from the stomach. This is probably due to a relatively unstable condition of certain central nervous mechanisms rather than to actual absence of the hunger tonus and hunger contractions of the empty stomach, although there are unquestionably great individual variations in the latter, even in comparatively healthy persons. The question can be settled by direct test on persons who claim to feel weakness but no gastric hunger pangs in starvation.
We think most observers will agree that in the normal person the hunger experienced 4 to 10 hours after a meal is primarily the gastric gnawing pangs, with practically no feeling of weakness, and no marked or obvious hyperexcitability of the brain and spinal cord. This is the justification for calling the gastric sensation the primary and essential factor in the hunger complex. Let us now consider the cause of the accessory hunger phenomena, and their relation to the gastric hunger pangs.