The liquid in the mouth is a mixture of the secretion of the salivary glands with that of the small, purely mucous glands.

It is a slightly turbid, tasteless fluid, of a distinctly alkaline reaction, of 1004-1008 specific gravity, and so tenacious that it can be drawn into threads. The amount secreted by an adult human being during 24 hours varies greatly according to circumstances, and has been variously estimated by different authors, by whom the wide limits of 200-2000 grms. (7-70 oz.) have been assigned as the daily amount.

Saliva contains about.5 per cent, of solids. Of these the greater part are organic; namely (1) Mucin, from the submaxillary, sublingual and small mucous glands, which can be precipitated by acetic acid. To this substance the viscidity of the saliva is due. (2) Traces of albumin, precipitable by concentrated nitric acid and boiling. (3) Traces of globulin, precipitated by carbonic acid. (4) Ptyalin, a peculiar ferment.

The inorganic constituents are salts, among which an inconstant amount of potassium sulphocyanate is found, a substance which does not exist in the blood.

There are also many morphological elements; of these the majority are accidental, being the remains of food, etc.; others are more or less characteristic; namely, (1) Salivary corpuscles, which are rounded protoplasmic masses containing nuclei and coarse granules which show Brownian movements. (2) Epithelial scales, from the surface of the mucous membrane of the mouth. (3) Various forms of bacteria, which propagate readily amid the decaying particles of food in the mouth. No bacteria or other fungi exist in ihe ducts of the glands or saliva taken from the ducts with the necessary aseptic precautions.