Globule leucocytes in the tracheal epithelium of rats

Globule leucocytes are described in the tracheal epithelium of young and adult rats. They do not appear in newborn rats up to 4 weeks. Globule leucocytes migrate through the epithelium to be found free in the tracheal lumen. They seem to be retarded a certain time in the apical part of the epithelium. The inclusions of the globule leucocytes are divided into four types. The different steps in the formation and transformation process of these inclusions are suggested. The electron-dense content of the inclusions is digested by pepsin, indicating that they contain protein. This result is not conflicting with the opinion that the globule leucocytes should contain immunoglobulins.