Ordinary mixed saliva may be easily collected by chewing some insoluble material, such as a bit of rubber tubing, and collecting the fluid which the motion causes to be poured into the mouth.

The collection of the secretion of the different glands requires more delicate methods. It may be collected separately by placing a cannula in the duct of each gland.

The form elements from mixed saliva from tip of tongue.

Fig. 63. The form elements from mixed saliva from tip of tongue, showing (e) large, irregular, scaly epithelial cells, (c) round salivary corpuscles, several (b) bacteria and (m) micrococci.

Parotid saliva obtained in this way is found to have no structural elements nor mucus, and is a thin fluid dropping easily, not capable of being drawn into threads. It contains some serum, albumin and globulin, potassium sulphocyanate, and ptyalin. The portion first secreted is commonly acid, and it never becomes strongly alkaline. Its specific gravity is 1003-1004. On standing it becomes turbid from the precipitation of carbonate of lime, which existed as bicarbonate.

The submaxillary secretion is more strongly alkaline than that of the parotid; it contains structural elements and mucin, but is not so viscid as the general mouth fluid.

The sublingual is much more viscid than either of the others, is more strongly alkaline, and contains much mucus and many salivary corpuscles.