Diagram illustrating the relationships between the olfactory receptors in the nasal mucosa and neurons in the olfactory bulb and tract. Cells of the anterior olfactory nucleus are found in scattered groups caudal to the olfactory bulb. Cells of the anterior olfactory nucleus make immediate connections with the olfactory structures via the anterior commissure. Inset: diagram of the olfactory structures on the inferior surface of the brain. (From Adams, Victor, Ropper 1997, with permission.)