To some saliva scientists, the human fluid is the main fascination. Others have dedicated their careers to comparing the glands of different creatures: spiny anteaters, bats, opossums, you name it. The glands are all so distinct, exalts Bernard Tandler, comparative anatomist at Texas Tech University in Lubbock.
They're distinct in size: The elephant's two main glands--the parotid glands--weigh more than 40 pounds apiece; those of little shrews and tiny bats weigh less than one-tenth of an ounce. But glands are also distinct in structure and function. Each creature, Tandler says, makes saliva tailored to its own unique needs.
The spit of a boar, for instance, contains testosterone to pique a sow's interest when it's showered over her during courtship. The spit of the short-tailed opossum contains chemicals used to mark its trails and territories.
The spit of a small bird, the swiftlet, contains a gummy glue that sticks its nest together (and is prized in Chinese cuisine for making bird's nest soup).
