Saliva
Saliva is filtered blood, "These observations are consistent with the fact that saliva is a filtrate of blood, meaning that the contents of blood—water, salts and macromolecules—pass through capillary walls into the salivary glands."  Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2741028/#:~:text=These%20observations%20are%20consistent%20with,walls%20into%20the%20salivary%20glands.