An eosinophilic substance is usually observed in the mouse nasal septum, and its volume increases with age. In contrast to descriptions in textbooks defining the eosinophilic substance as amyloid, our previous report revealed that the observed eosinophilic substance is not amyloid, but consisted of collagen and an amorphous material. Furthermore, it was suggested that the amorphous material was produced by the clear hematoxylin and eosin (HE)-stained nasal gland epithelial cells. In this study, we investigated the deposition process of the amorphous material produced by nasal gland epithelial cells in the interstitium morphologically. In most cases, the amorphous materials in the clear HE-stained nasal gland epithelial cells accumulated at the basal portion. Collagen fibers surrounding the nasal glands partially disappeared, whereas the amorphous material in contact with the rough endoplasmic reticulum of the nasal gland epithelial cells continued to the amorphous material in the interstitium. These findings suggested that the amorphous material produced by the clear HE-stained nasal gland epithelial cells migrated to the interstitium through the partial opening of the basement membrane.