The reference to "overstudy" refers to the evenings young Thomas spent poring over medical textbooks after he came home from work, until madness took hold.
He no longer abused himself with short sleep, overwork, and overstudy.
And now, before I take up my tale, I want to anticipate the doubting Thomases of psychology, who are prone to scoff, and who would otherwise surely say that the coherence of my dreams is due to overstudy and the subconscious projection of my knowledge of evolution into my dreams.
I tend to doubt that the abscess was actually caused by overstudy, but this was a century ago.
Those who deny the possibility that the death was caused by overstudy are obviously unfamiliar with the term “Karōshi”.