(at around 36 mins) Holmes idly picks up the newspaper and looks through it. His attention is immediately caught by the headline of 'Monkey Theft.' It makes mention of the 'Lonon Zoo', when it should be London Zoo.
Near the end, Holmes gives Lestrade the Professor's syringe case. As Holmes picks up the case, a newspaper is revealed underneath with the headline "SCOTLAND YARD SOLVES MONKEY MYSTERY". The text below the headline, however, is taken from Walter Scott's 1824 novel "Redgauntlet."
As Holmes is shuffling through papers on Professor Presbury's desk, one of the documents shown is a statement by Dr John H Watson concerning the post-mortem examination of the Honorable Ronald Adair. This is a reused prop from the 1986 episode "The Empty House" from "The Return of Sherlock Holmes."
It's not entirely clear, but it appears that actress Sarah Woodward (Edith Presbury) is trying not to laugh in the final scenes of this caper when she beholds her father's ape-like behavior. Her close-up shows a near-smile and the next frame shows her burying her head in her fiance's chest, as if to hide her laughter.
When discussing the recent monkey thefts Lestrade mentions, among several special of apes, that a gorilla has been stolen. This wouldn't have been possible as there were no proper scientific research on gorillas until the 1920s and they would not have appeared in zoos until several decades later.
Although the original Conan Doyle story was written in 1923, the story itself is set some time in the late Victorian period (poss. very early Edwardian) just prior to Holmes' retirement in 1903.
Although the original Conan Doyle story was written in 1923, the story itself is set some time in the late Victorian period (poss. very early Edwardian) just prior to Holmes' retirement in 1903.