"The hunt had become a monomania with him.

It had become an obsession.

He had given his whole mentality to it and it had absorbed all his faculties.

He was now the victim of it.
He had grown powerless in the grip of the idea; he had lost volition in the matter.
"You can imagine my consternation when I realized this.

I began to fear the day when his insanity would take some violent form and he would endeavor to do me a personal injury.