Gull's musings upon the nature of the right brain and its relationship to consciousness are in keeping with what is known of Gull's interests during the last few years of his life.
According to [William Withey Gull:] A Biographical Sketch, Gull's final researches were directed towards an exploration of the right brain, and thus the ruminations here would seem to be in character.
And yes, by that time researchers such as Broca and Wernicke had begun to identify the phenomenon of brain function lateralization, specifically with regard to speech production (in what's now called "Broca's area") and language comprehension (in what's now called "Wernike's area"). Mid-twentieth century research on epilepsy and on split-brain surgery patients fleshed out our understanding of this phenomenon, but the groundwork was in place by Gull's time.