These are four small, gland-like bodies situated along the posterior inner edges of the lateral lobes of the thyroid gland, usually two on a side. They seem to be of great importance in the metabolism of the body. When removed fatal tetany results. This is characterized by convulsions, spasmodic contractions, rapid and labored respiration and salivation. These may be due to disturbances of the calcium metabolism, or to the presence within the circulation of a toxin that is normally neutralized by the parathyroid activities.