The writer of these lines is trying to give good advice and is encouraging the idea of positive thinking and intrinsic value. He is saying that the essence of an object's value or goodness always remains and cannot be sullied by other less valuable or humble things pasing across it or near it. He gives examples. Firstly there is the highly attractive plant and herb called Basil. This plant is highly valued for its aromatic qulaities, for its flavour and for its beauty, as its glossy, bright green leaves are lovely to look at. The writer is saying that these qualities do not disappear just because a beetle crawls over one of the plant's leaves. In the same way, a royal residence does not lose its worth because of a few insects and perhaps cobwebs. Cowrie shells will always be coveted for their prettiness and can be exchanged for other things and as for pearls - well, they are always beyond price because of their rarity, lucent colour and alluring sheen. People of integrity should hold their heads up high, no matter what others around them may do.