when the eyes and back turn upward from the desk, when the human engine waits

The human body is compared to a machine, to a motor car and although the image of Nature as a machine (something that can be known and controlled) isn’t new, the comparison is between life of men and the motor of a taxi waiting.
This image precedes Tiresias’ vision. Tiresias, who had the experience of both sexes is said to be throbbing between two lives, like the motorcar.

Tunnel, Valencia.