As a very long highway goes to two places, to one at the beginning, and to another at the end, so do the rays of the sun go to both worlds, to this one and to the other. They start from the sun, and enter into those arteries; they start from those arteries, and enter into the sun.

In plain words: Like a long road that reaches two towns, one at each end, the sun's rays reach both this world and the other. They go from the sun into the heart's channels and from those channels back to the sun.