Answer:
The metaphor he uses is "this chopping of civilized life", in which he means that you are forced along whatever current is controlling you and you have no control. A similar metaphor is located in lines 199-209, which are "the surface of the Earth" and "the path which the mind follows". Just like the first one talks about how you are controlled by an established current, these show that the human mind is easily influenced similar to how the Earth's ground is easily shaped and marked by the steps taken by otehrs. These state issues of non-individuality and how we don't develop our own ideas.