Distribution, location, and shape of the mucous glands in 20 tracheas were systematically studied and analyzed. The specimens were treated by whole-mount methods by which the entire mucosa was separated from the submucosa and each layer stained and studied separately. In the cartilaginous layer the mucosa was found to contain no gland mass, the glands being situated exclusively in the submucosa. In the membranous wall the glands are disposed in several layers. The mucosa contains only 35 to 50 glands in the superior quarter, while in the transverse tracheal muscle there is a layer of 120 to 140 glands. The greater part of the glands are dorsal to the muscle where the glands are arranged in two layers. The distribution and shape of the glands are characteristic for each layer and are dependent upon the anatomical events during their development.