Why is saliva called “Yu Ye” (juice of jade)?

In ancient China, our Chinese ancestors called our sublingual part “Xun Ying” in Chinese. There were two apertures; the left one was called “Jin Jing” (the juice of excellence) and the other one was called “Yu Ye” (the juice of jade). When the essence of the body ran to the “Yu Chi” (the pond of jade), formally called oral cavity, the two apertures would secrete saliva so it was called “Yu Ye” (the juice of jade). 

This juice was extraordinary. According to the ancients, the juice was essential to dredge the pulse and the flow of blood, glow one’s skin, strengthen bones and teeth and prevent the hair from turning grey. From the above, it is not difficult to sense that the ancients treated saliva priceless.