Physical Boundary

Every living thing has a physical boundary that separates it from its ex-ternal environment. Beginning with the bacteria(细菌) and the simple cell and ending with man, every organism has a certain limit which marks where it begins and ends.Anyone who has had experience with dogs, particularly in the country-side such as on farms, is familiar with the way in which the dog handles space. In the first place, the dog knows the limits of his master蒺s “yard”and will defend it against encroachmen…