A completely different theory holds that yawning assists in the physical development of the lungs early in life, but has no remaining biologicalfunction in adults.
另一种完全不同的理论认为，打呵欠有助于生命早期肺部的生理发育，但对成年人没有任何剩余的生理功能。
2
This paper reviews the structure, source, biologicalfunction of cecropins and their application in plants and animals, and discuses their existing problems and perspectives.