All of the following are constituents of saliva EXCEPT

Saliva is secreted by the salivary glands and contains water, electrolytes like sodium, potassium, chloride, and bicarbonates, along with enzymes such as salivary amylase and lysozyme.

Rennin is a proteolytic enzyme found in the gastric juice of infants, which helps in the digestion of milk proteins. It is not a constituent of saliva.

Answer: rennin