Organs of Nutrition 119 
Many birds carry in their beaks the grasses and 
twigs with which they construct their nests, and if a sticky 
fluid helped them to get their food, why would it not 
also soften the twigs and make them easy to bend? Not 
only this, but certain birds, such as our Chimney Swifts, 
are provided with saliva in such quantities, and of such 
tenacious consistency, that the entire nest—a mosaic of 
Fic. 91.—Nest of Esculent Swiftlet (edible bird’s nest) composed entirely of saliva. 
small twigs, each about an inch in length—is set in saliva 
cement, and fastened to the vertical side of a chimney 
or charred tree-trunk by the same means. Even this is 
only a step, or link, in the direction of the extreme use- 
fulness of saliva, for the little East Indian birds known 
as Swiftlets (one of which ornithologists call Collocalia 
juciphaga) make their nests entirely of saliva or mucus. 
The second part of the scientific name, which means an 
eater of seaweed, refers to the idea formerly held, that 
