Final answer:
The substance inside of a ranula is mucous. It is a mucus-filled cyst that is typically sterile unlike purulent material indicating infection.
Step-by-step explanation:
The substance inside of a ranula is mucous, not purulent. A ranula is a type of mucocele, which is a mucus-filled cyst that can occur in the mouth, usually under the tongue. It is formed when a minor salivary gland becomes blocked, leading to an accumulation of mucus. In contrast to purulent material, which is comprised of pus and indicates infection (commonly seen with bacterial involvement such as in abscesses or certain infections like bacterial rhinosinusitis), the clear or bluish swelling of a ranula contains mucus and is typically sterile.