This quote comes when Peregrinus is using a microscope that allows him to observe people’s thoughts from the motion of their physical brain and nerves.
It may finally be remarked that as a result of his observations through the microscope Peregrinus suffered great embarrassment from many people. These people were the young men who were constantly being carried away by rapturous enthusiasm and letting loose torrents of sonorous cliches. The most profound and sonorous among them were young poets, brimming over with imagination and genius, who had to endure a great deal of adulation, especially from ladies. There were also literary women, who knew all the depths of sublunary existence, as the phrase goes, like the backs of their hands; they also held penetrating philosophical views on the constitution of society, and could deliver these in eloquent language, like an Easter sermon. If Peregrinus had been astonished to see the silver threads in Gamaheh’s brain twining into an invisible region, he was no less amazed at what he beheld in the brains of the people just mentioned. He saw the strange network of veins and nerves, but noticed also that when these people talked with exceptional eloquence about art and learning and the main currents of intellectual life, their veins and nerves did not penetrate into the recesses of their brains, but curved back, so that it was impossible to discern their thoughts with any clarity. He communicated this observation to Master Flea, who was sitting as usual in a fold of his neckerchief. Master Flea remarked that what Peregrinus had mistaken for thoughts were nothing more than words, vainly endeavouring to become thoughts.