During his stay in Amsterdam, Steno discovered a previously undescribed structure, the "ductus stenonianus" (the duct of the parotid salivary gland) in sheep, dog and rabbit heads.
Selama menetap di Amsterdam, Steno menemukan struktur yang belum dideskripsikan sebelumnya, "ductus stenonianus" (duktus kelenjar liur parotid) pada kepala domba, anjing dan kelinci.