how does jarvis lorry appear as a psychiatrist in book 2 chapter 19?

In Part II, Chapter Nineteen, on the tenth morning, Mr. Lorry finds Doctor Manette behaving normally again. Mr. Lorry and Miss Pross decide to proceed as if nothing had happened, but Mr. Lorry presents the Doctor's own case to him as if it were someone else. The Doctor realizes that he has been shoemaking by looking at his own blackened hands, and he acknowledges that his shoemaking equipment should be taken away from him--but without his knowledge. He also explains to Mr. Lorry that "the patient" (himself) is not able to remember what happened during his relapses, and that continuing his professional activities will not affect his condition.